ttrmitg 


Division 

Range 

Shelf..- 

Received... 


A  MANUAL 


or 


CHEMISTRY, 

ON   THE   BASIS    OF 

TURNER'S  ELEMENTS  OF  CHEMISTRY", 

CONTAINING,  IN  A  CONDENSED  FORM, 

ALL  THE  MOST  IMPORTANT  FACTS  AND  PRINCIPLES 
OF  THE  SCIENCE. 


DESIGNED   AS   A   TEXT-BOOK 

FOR  COLLEGES  AND  OTHER  SEMINARIES  OF  LEARNING. 


Titian. 

REWRITTEN  AND  RESTEREOTYPED,  WITH  MANY  NEW  ILLUSTRATIONS. 


BY  JOHN  JOHNSTON,  LL.  D., 

PROFESSOR   OF  NATURAL   SCIENCE   IN  THE   WESLEYAN   UNIVERSITT. 


PHILADELPHIA: 

CHARLES    DKSILVEK, 

1229  CHESTNUT  STREET. 

BALTIMORE :  CUSHINGS  &  BAILEY. 
1863. 


Entered,  according  to  Act  of  Congress,  in  the  year  1856,  by 
CHARLES   DESILVER, 

in  the  Clerk's  Office  of  the  District  Court  of  the  United  States  for  the  Eastern  District 
of  Pennsylvania. 

gT£BXOTTP£D  BY  J.  PAOAII. 


TO 

PARKER  CLEAYELAND,  LL.D., 

PROFESSOR   OP   CHEMISTRY,   MINERALOGY,   AND   NATURAL   PHILOSOPHY, 

IN  BOWDOIN  COLLEGE,  BRUNSWICK,  ME.; 
DISTINGUISHED  NO  LESS  FOR  HIS  PERSONAL  VIRTUES 

THAN 

AS  THE  AUTHOR 

OF  THE  FIRST  AMERICAN  WORK  ON  MINERALOGY  AND  GEOLOGY 

£lje  follotofnfl  3Paaes  are  aaespecttullg  Enacrflbetr, 

Dl   TOKEN   OP   THE   DEEP   SENSE    OP   OBLIGATION  ENTERTAINED 
BY  HIS   FRIEND  AND  FORMER  PUPIL, 

JOHN  JOHNSTON. 

»  . 

(itt) 


PREFACE 

\ 

TO   THE   PRESENT,   OR  SIXTH  REVISED   EDITION 


BY  the  original  contract  between  the  publishers  and 
compiler  of  this  work,  provision  was  made  for  a  periodical 
revision,  in  order  that  new  and  important  discoveries  might 
be  introduced  without  delay,  and  the  work  be  made  to 
conform  as  much  as  possible  to  the  rapidly  advancing 
science.  These  revisions  have  been  carefully  attended 
to,  and  considerable  alterations  in  the  plates  from  time 
to  time  have  been  required;  the  whole  of  the  part  on 
Organic  Chemistry,  in  the  last  preceding  revision,  having 
been  rewritten  and  restereotyped. 

But  the  progress  of  the  science  is,  and  has  been,  still 
onward ;  —  new  and  important  facts  have  rapidly  been 
made  known,  and  new  views,  throwing  more  or  less  light 
on  points  heretofore  considered  obscure  and  doubtful,  have 
4)een  proposed ;  so  that  in  the  present  revision  an  entire 
recast  of  the  work  has  been  found  necessary.  Encouraged 
by  the  favor  heretofore  sKown  the  work,  the  publisher  has 
cheerfully  incurred  the  expensed  stereotyping  it  anew, 
including  the  preparation  of  many  new  illustrations ;  and 
the  results  of  our  joint  labors  are  here  presented  to  the 
public  in  a  book  substantially  new,  though  retaining  the 
former  title. 

The  changes  which  have  been  made  are  too  great  and 
important  to  be  discussed  here ; — for  a  knowledge  of  them 
i*  (v) 


VI  PREFACE. 

the  intelligent  reader  is  referred  to  the  pages  of  the  work 
itself;  they  are  such  only  as  the  new  aspects  of  the  science 
seemed  imperatively  to  demand.  The  principles  which 
have  been  followed  in  its  preparation  are  indicated  in  the 
extracts  from  the  advertisements  to  former  editions,  which 
will  be  found  further  on.  Many  of  the  new  cuts  have 
been  derived  from  the  profusely  illustrated  work  of  Reg- 
nault ;  others  are  original,  or  have  been  obtained  from 
miscellaneous  sources. 

The  Grouping  of  the  Elements  adopted  is  nearly  the 
same  as  that  of  Gmelin ; —  it  is  not  free  from  objection, 
but  is  considered  the  best  yet  proposed  on  this  difficult 
point.  In  preparing  the  remarks  introductory  to  the  part 
on  Organic  Chemistry,  important  aid  has  been  derived 
from  Dr.  W.  Gibbs'  "  Report  on  the  Recent  Progress 
of  Organic  Chemistry,"  prepared  for  the  American  Asso- 
ciation for  the  Advancement  of  Science,  and  printed  in 
the  Proceedings  of  their  ninth  Meeting,  at  Providence, 
B.  L,  August,  1855. 

Many  thanks  are  due  to  teachers  and  other  kind  friends, 
for  judicious  suggestions  and  encouraging  words  during 
the  preparation  of  the  work ;  and  it  is  now  offered  to  the 
public  in  the  confident  expectation  that  it  will  be  found,, 
not  less  adapted  for  use  in  the  school  or  lecture-room  than 
preceding  editions. 

MlDDLETOWN,  CT.,  July,  1856. 


EXTRACT  FROM  THE  ADVERTISEMENT  TO  THE  FIRST  EDITION,    (1840.) 

THE  preparation  of  the  following  pages  was  undertaken  by  the  advice  .of  the 
late  lamented  President  of  the  Wesleyan  University,  with  the  primary  design 
of  providing  a  suitable  Text-book  on  Chemistry,  for  the  use  of  the  annual 
classes  in  that  institution.  • 

There  are  indeed  already  before  the  public  many  excellent  works  on  this 
branch  of  science,  the  great  merits  of  which  the  subscriber  is  happy  to  acknow- 
ledge; but  he  long  since  became  convinced,  from  his  experience  in  teaching, 
of  the  need  of  a  work  of  a  little  different  character,  for  the  special  use  of  students 
in  our  higher  seminaries  of  learning,  as  a  text-book.  The  object  of  a  great 
majority  of  students,  even  of  those  who  pursue  a  collegiate  course,  is,  not  tt 
make  themselves  familiar  with  minute  details  of  facts  or  processes  of  mani- 
pulation, but  to  understand  the  great  principles  of  the  science,  and  the  leading 
facts  which  serve  for  its  foundation.  To  facilitate  the  accomplishment  of 
this  purpose  is  the  object  of  the  present  work.  In  preparing  it,  the  excel- 
lent "Elements  of  Chemistry"  of  the  late  Dr.  Turner  has  been  adopted  as  the 
basis,  and  all  of  that  work  incorporated  in  it  which  was  suited  to  our  purpose. 
Ills  arrangement  has  been  uniformly  followed,  with  a  few  unimportant  excep- 
tions, which  it  is  not  necessary  here  to  particularize.  This  arrangement,  on 
the  whole,  is  considered  the  best  that  has  ever  been  proposed. 

The  part  of  Dr.  Turner's  work  omitted  is  taken  up  chiefly  with  details  of  facts 
and  discussions  of  opinions  and  theories,  which  indeed  is  important  in  a  work 
designed  for  the  general  student,  but  which  would  be  out  of  place  in  a  book 
prepared  expressly  to  be  used  as  a  text-book.  Its  place,  however,  has  been 
in  part  supplied  by  matter  compiled  from  various  other  sources,  so  that  the 
work  is  thought  to  be  sufficiently  large  for  the  ordinary  use  of  students,  as  the 
study  of  this  science  is  usually  pursued  in  this  country.  It  has  constantly  been 
an  object,  while  the  work  should  be  true  to  the  science,  and  present  in  true 
proportion  all  its  important  features,  to  make  it  at  the  same  time  as  practical 
as  possible ;  to  lead  the  student  to  apply  the  principles  he  learns  to  the  solu- 
tion of  natural  phenomena,  or  processes  he  may  witness  in  the  arts. 


EXTRACT  FROM  THE  ADVERTISEMENT  TO  THE  SECOND  EDITION, 
IN  the  present  edition  the  work  hasjjeen  carefully  revised,  and  indeed  re- 
compiled from  the  seventh  edition  of  Turner's,  and  many  additions  made  to 
adapt  it  to  the  advancing  state  of  the  science.  *  *  *  * 

The  extracts  from  other  authors  are  always  introduced  in  their  own  lan- 
guage, except  in  cases  where  it  was  necessary  to  make  some  little  change  to 
incorporate  the  extract  the  better  with  the  passage  with  which  it  comes  in 
connection.  In  a  few  instances  the  names  of  authors  are  introduced  in  the 
text.  To  avoid  the  necessity  of  constantly  introducing  quotation  marks  and 
references,  a  list  of  the  authors  which  have  been  used  will  be  given. 

To  facilitate  the  acquisition  of  the  science,  the  text  is  divided  into  paragraphs, 
and  numbered;  and  references  to  important  facts  and  principles  introduced  as 
frequently  as  they  seemed  necessary.  As  in  many  institutions  so  much  time 
cannot  be  devoted  to  this  science  as  would  be  requisite  for  a  thorough  study 
of  the  whole  work,  the  less  important  parts  have  been  printed  in  smaller  type, 
which  may  be  omitted  on  the  first  reading.  The  intelligent  student,  however, 
it  is  hoped,  will  not  be  satisfied  without  a  perusal,  at  his  hours  of  leisure, 
of  the  whole  work.  (vii) 


LIST  OF  WORKS 

MADE  USE  OF,  MORE  OR  LESS,  IN  THE  PREPARATION  OF  THIS  WORK. 


Elements  of  Chemistry,  by  the  late  Edward  Turner,  M.D.,  F.R.S.,  Ac.,  edited  by 
J.  Liebig,  M.  D.,  Ph.  D.  F.  R.  S.,  &c.,  and  Wm.  Gregory,  M.  D.,  F.  R.  S.  E. 
Elements  of  Chemistry,  &c.,  by  Robert  Kane,  M.D.,  M.R.I.A.,  &c.    Dublin. 
Chemistry  of  Organic  Bodies,  by  Thomson. 
Do.  Inorganic  Bodies.    Two  vols. 

Ure's  Dictionary  of  Chemistry.    Two  vols. 

Encyclopedia  Metropolitana.    Articles,  Electro-magnetism,  Electricity,  Galvanism,  Heat, 
Light,  and  Chemistry. 

Library  of  Useful  Knowledge.    Articles,  Electricity,  Galvanism,  Magnetism,  Electro- 
magnetism,  Chemistry,  &c. 

Thomson's  Outlines  of  the  Sciences  of  Heat  and  Electricity. 

Traite  de  Chimie  Appliquee  aux  Arts,  par  M.  Dumas.     Six  tomes. 

Traite  de  Chimie,  par  J.  J.  Berzelius ;  traduit  par  Me.  Esslinger.    Huit  tomes. 

Abreg6  Eleinentaire  de  Chimie,  par  J.  L.  Lassaigne.    Deux  tomes. 

Organic  Chemistry  in  its  applications  to  Agriculture  and  Physiology,  by  Liebig,  edited 
by  Webster. 

Animal  Chemistry,  or  Organic  Chemistry  in  its  applications  to  Physiology  and  Pathology, 
by  Liebig. 

Lectures  on  Agricultural  Chemistry  and  Geology,  by  J.  F.  W.  Johnston. 

Elements  of  do.  do. 

Thomson's  "  First  Principles."    Two  vols. 

Prof.  Silliman's  Chemistry.    Two  vols. 

Prof.  Hare's  Compendium  of  Chemistry. 

Faraday's  Chemical  Manipulation,  edited  by  Dr.  J.  K.  Mitchell. 

Thomson's  History  of  Chemistry.    Two  vols. 

A  Treatise  on  Chemistry  by  Michael  Donovan,  Esq.;  Lardner's  Cabinet  Cyclopedia. 

Prof.  John  W.  Webster's  Manual  of  Chemistry,  on  the  basis  of  Prof.  Urande's. 

United  States'  Dispensatory,  by  Drs.  Wood  and  Bache. 

American  Journal  of  Science  and  the  Arts,  conducted  by  Prof.  Sillimaa. 

Henry's  Elements  of  Chemistry.    Three  vols. 

Cleaveland's  Mineralogy  and  Geology. 

Dana's  Mineralogy. 

Shepherd's  Mineralogy.    Three  vols. 

Griffin's  Chemical  Recreations. 

Journal  of  the  Franklin  Institute. 

Parke's  Chemical  Catechism. 

Chaptal's  Chemistry  applied  to  Agriculture. 

Elements  of  Chemistry,  by  M.  Lavoisier,  translated  from  the  French  by  R.  Kerr,  F.  R.  S. 

Watson's  Chemical  Essays.    Five  vols. 

Noad's  Chemical  Manipulation  and  Analysis. 
Do.    Lectures  on  Electricity. 

Knapp's  Chemical  Technology.    Vols.  I.,  II. 

Gibbs'  Report  on  the  Recent  Progress  of  Organic  Chemistry. 

Gmelin's  (L.)  Hand-book  of  Chemistry,  translated  by  Henry  Watts.    Vols.  I.  to  IX. 

Traite  de  Chimie  Elementaire.  Theorique  et  Pratique,  par  L.  J.  Thenard.     Cinq  tomes, 

Cours  de  Chimie  Elementaire,  par  A.  Bouchardat.    Deux  tomes. 

Lemons  sur  la  Philosophie  Chimie,  professes  an  College  de  France,  par  M.  Dumas. 

Theorie  des  Proportions  Chimiques,  et  Table  Synoptique  des  Poids  Antomiques,  etc., 
par  J.  J.  Berzelius. 

Trnite  de  Mineralogie,  par  M.  L'AbbS  Haiiy.    Quatre  tomes. 

Elements  de  Physique,  etc.,  par  M.  Pouillet.  do. 

Lehrbuch  der  Chimie,  von  E.  Mitscherlich,  Berlin,  1844. 

Orundriss  der  Chimie,  von  Professor  Dr.  F.  F.  Runge. 

Cours  de  Chimie  Generale,  par  J.  Pelouze  et  E.  Fremy.  Trois  tomes,  accompagne"  d'un 
Atlas  de  46  Planches. 

Gcrhardt  (Ch.),  Trait6  Chimio  Organique. 

Regnault,  Cours  Klementaire  do  Chimie. 

The  same,  translated  into  English  by  Dr.  T.  F.  Betton,  M.  D. 

Besides  the  above,  reference  has  often  been  made  to  various  other  works,  as  Le  Diction- 
naire  des  Sciences  Naturelles,  Annales  de  Chimie  et  de  Physique,  the  various  Encyclopedias, 
Philosophical  Transactions,  &c. 

(viii) 


CONTENTS. 

PAET  I 

THE  IMPONDERABLE  AGENTS. 

PAOB 

INTRODUCTION , 13 

I.  HEAT. 

Nature  and  Sources  of  Heat 17 

Expansion  of  Bodies  by  Heat «...  18 

Thermometers 22 

Distribution  of  Heat 29 

Relation  of  Heat  to  Changes  in  the  State  of  Bodies 36 

Specific  Heat. — Capacity  of  Bodies  for  Heat 58 

II.  LIGHT. 

Nature  and  Sources  of  Light 60 

Distribution  of  Light 65 

Decomposition  of  Light 68 

III.  ELECTRICITY. 

Nature  of  Electricity. — Electrical  Theories 74 

Distribution  of  Electricity 76 

Sources  of  Electricity 81 

Galvanism 88 

Effects  of  Galvanic  Electricity '102 

Electro-magnetism Ill 

PART  II. 

GENERAL  CHEMISTRY. 

The  Elements.— Chemical  Affinity 137 

Laws  of  Combination. — Atomic  Theory 143 

Nomenclature  of  Chemistry. — Symbols ....v 151 

Crystalography 168 

<M 


CONTENTS. 


PART  III. 

SPECIAL  CHEMISTRY  — INORGANIC. 

PAG« 

CLASSIFICATION  OF  ELEMENTS 172 

METALLOIDS,  OR  NON-METALLIC  ELEMENTS 173 

GROUP  I.  —  Oxygen 174 

Hydrogen 181 

Nitrogen 191 

GROUP  II.  —  Chlorine 206 

Iodine 215 

Bromine 213 

Fluorine 220 

GROUP  III. — Sulphur 222 

Selenium 239 

Tellurium , 240 

GROUP  IV. — Phosphorus 241 

Arsenic .. 250 

Gaoup  V.  —  Carbon 257 

Silicon 278 

Boron 281 

THE  METALS 284 

GENERAL  PROPERTIES 284 

GROUP  I. —Potassium , 298 

Sodium 310 

Lithium 318 

Ammonium , 319 

GROUP  II.  —  Barium 328 

Strontium 330 

Calcium 331 

'     Magnesium 337 

GROUP  III. — Aluminum 339 

Glucinum 344 

Zirconium 344 

Thorium 344 

Yttrium 344 

Erbium 344 

Terbium 344 

Cerium 344 

L&nthanum. 344 

Didymium 344 


CONTENTS.  XI 

PAGE 

GROUP  IV. — Manganese 345 

Iron . 348 

Chromium 357 

Zinc 359 

Cadmium 362 

Tin 362 

Cobalt 364 

Nickel , 365 

GROUP  V.— Antimony 365 

Bismuth 367 

Lead..:. 368 

Copper , 371 

Vanadium 373 

Molybdenum 373 

Tungsten 373 

Titanium _., 373 

Uranium .«rfT.. .!...... 374 

Columbium 374 

Tantalum 374 

GROUP  VI.— Mercury 374 

.  Silver... 381 

Gold 386 

Platinum 389 

Osmium 391 

Iridium , 392 

Palladium... 392 

Khodium 392 

Kuthenium ..  392 


PART  IV. 

SPECIAL    CHEMISTRY— ORGANIC. 

GENERAL  PROPERTIES  OP  ORGANIC  BODIES 393 

STARCH,  SUGAR,  GUM,  LIGNINE «, 405 

Starch,  or  Fecula ,. 405 

Sugars , 408 

Gums , 411 

Woody  Fibre,  Lignine,  Cellulose 412 

ALCOHOLS  AND  SUBSTANCES  DERIVED  FROM  THEM 418 

Wine  Alcohol v 418 

Methylic  Alcohol,  or  Wood  Spirit 428 

Amylic  Alcohol 430 

Sulphur  Alcohols,  OF  Mercaptans. 432 


X  CONTENTS. 

MM 

ETHERS. — COUPLED,  OR  VINIO  ACIDS 433 

Ethers  of  Wine  Alcohol 434 

I.  Simple  Ethers 434 

H.  Compound  Ethers, 438 

Ethers  of  Methylio  Alcohol 440 

I.  Simple  Ethers 440 

f  II.  Compound  Ethers 442 

Ethers  of  Amylic  Alcohol 443 

VOLATILE,  OR  ESSENTIAL  OILS 444 

Carbohydrogen  Volatile  Oils..* 446 

Oxygenated  Volatile  Oils 448 

Sulphuretted  Volatile  Oils 452 

Camphors 453 

Coumarine , 454 

FIXED  OILS  AND  FATS 455 

Glycerine 456 

Stearine  and  Stearic  Acid 457 

Margarine  and  Margaric  Acid 458 

Oleine  and  Oleic  Acid 458 

Other  Proximate  Principles  of  the  Fats 459 

Soaps  and  Plasters ; 462 

RESINOUS  SUBSTANCES 463 

VEGETABLE  ACIDS  NOT  INCLUDED  IN  PRECEDING  GROUPS 465,, 

ORGANIC  ALKALIES,  OR  ALKALOIDS 469 

ALKALOIDS  OF  THE  ETHERS,  OR  CONJUGATED  AMMONIAS 471 

ORGANIC  COLORING-MATTERS 475 

THE  AMIDES  AND  NITRILES 478 

CYANOGEN  AND  ITS  COMPOUNDS 480 

Compounds  of  Cyanogen  and  Oxygen 481 

Compounds  of  Cyanogen  and  Hydrogen 484 

Sulphocyanates  or  Sulphocyanides 485 

Compounds  of  Cyanogen  and  the  Metals 486 

Double  Cyanides. — Polycyanides 487 

ALBUMINOUS,  OR  PROTEINE  COMPOUNDS 490 

CHEMICAL  PHENOMENA  OF  VEGETATION 434 

COMPOSITION  OF  THE  ANIMAL  TISSUES 498 

THE  BLOOD. — PHENOMENA  OF  RESPIRATION  AND  DIGESTION 500 

The  Blood 501 

Phenomena  of  Digestion 503 

Phenomena  of  Respiration 500 

SEVERAL  ANIMAL  SECRETIONS  AND  EXCRETIONS  NOT  BEFORE  NOTICED  510 

APPENDIX. — TABLES  OF  WEIGHTS  AND  MEASURES 515 


MANUAL  OF  CHEMISTRY 
PART  I. 

THE   IMPONDERABLE  AGENTS. 


INTRODUCTION. 

1.  WE  recognize  as  matter  or  substance  whatever  possesses  the 
four  properties  of  extension,  impenetrability,  inertia,  and  gravity, 
or  weight.     By  the  first  of  these  properties  every  body  occupies  a 
portion  of.  space ;  by  the  second,  it  refuses  to  allow  another  body 

'to  occupy  this  space  at  the  same  time  with  itself;  by  the  third,  it 
is  incapable,  of  itself,  of  changing  its  state,  whether  of  rest  or 
motion  j  and  by  the  fourth,  if  unsupported,  it  falls  to  the  earth. 
Whatever  does  not  possess  all  these  properties  is  not  recognized  as 
matter. 

2.  Natural  science  embraces  the  whole  range  of  material  things : 
their  properties,  the  changes  they  are  capable  of  undergoing,  and 
the  laws  of  their  changes. 

3.  As  has  been  suggested  by  Grmelin,  all  the  changes  of  which 
any  portion  of  matter  is  capable  may  be  referred  to  the  three 
causes  or.  forces  of  Repulsion,  Attraction,  and  Vitality. 

4.  Repulsion  is  manifest  in  the  property  of  matter  denominated 
impenetrability,  and  in  the  expansion  of  bodies,  especially  by  the 
influence  of  heat,  as  will  be  shown  hereafter. 

QUESTIONS.  —  1.  What  is  matter  or  substance?  Define  "what  is  meant 
by  the  four  properties  mentioned.  —  2.  What  does  Natural  Science  em- 
brace ? — 3.  To  what  three  causes  may  all  changes  of  matter  be  referred  t 
~-  4.  In  what  ia  repulsion  manifest  ? 

'    2  (18) 


14  INTRODUCTION. 

5.  Attraction  manifests  itself  in  a  variety  of  forms :    1.  As 
Gravitation,  or  that  force  which  acts  at  all  distances,  however 
great,  and  between  the  largest  masses.     2.  Cohesion,  or  that  force 
which,  acting  only  at  distances  immeasurably  small,  unites  the 
parts  of  the  same  mass.     3.  Electrical  and  Magnetic  Attraction. 
4.    Chemical  Attraction  or  Affinity,  which  acts  only  at  insensible 
distances,  and  between  the  ultimate  particles  of  bodies,  and  pro- 
duces  homogeneous  compounds. 

6.  Vitality  is  that  peculiar  force  or  power,  possessed  both  by 
animals  and  plants,  by  which  the  simple  affinities  of  the  various 
substances  contained  in  their  bodies  are  so  modified  and  controlled 
in  their  action,  as  to  produce  the  complex,  and  almost  innumerable 
organic  compounds,  such  as  sugar,  woody-fibre,  albumen,  &c. 

Changes  produced  by  all  the  varieties  of  attraction  above  mentioned, 
except  the  fourth,  or  last,  pertain  properly  to  Physics  or  Natural  Philoso- 
phy ;  while  those  produced  by  Affinity,  either  alone,  or  as  it  is  controlled 
by  vitality  in  the  bodies  of  plants  and  animals,  belong  to  Chemistry. 

The  changes  produced  by  the  action  of  affinity  consist  in  the  combina- 
tion of  dissimilar  substances  into  a  homogeneous  mass,  or,  occasionally, 
the  separation  of  dissimilar  substances  from  a  homogeneous  mass.  We 
may,  therefore,  define  Chemistry  as  the  science  which  treats  of  the  com. 
bination  of  dissimilar  substances  into  homogeneous  compounds,  and  of 
the  separation  of  dissimilar  bodies  from  homogeneous  compounds. 

7.  Molecules  or  Atoms. — All  bodies,  it  is  believed,  are  made 
up  of  infinite  numbers  of  indefinitely  small  particles — too  small  to 
be  detected  by  the  eye,  even  when  aided  by  the  most  powerful 
microscopes — which  are  called  molecules  or  atoms  (from  a,  priva- 
tive, and  temnOj  I  cut),  indicating  their  supposed   indivisibility. 
Our  knowledge  of  them  is  obtained  indirectly,  as  we  shall  see 
hereafter;   but  it  is  believed  that  all  the  molecules  of  the  same 
substance  are  precisely  alike  in  weight,  size,  and  form,  as  well  as 
other  properties. 

8.  Simple  and  Compound  Bodies, — From  what  has  been  said 
above,  the  distinction  between  simple  and  compound  bodies  is 
obvious.     Simple  substances  are  such  as  are  believed  to  be  com- 

QUESTTONS. — 5.  What  are  the  different  varieties  of  attraction  ?  Define 
the  several  varieties.  —  6.  What  is  vitality?  What  changes  pertain  to 
Natural  Philosophy  or  Physics  ?  What  to  Chemistry?  The  changes  pro- 
duced by  the  action  of  affinity  consist  in  what  ?  —  7.  Of  what  are  all 
bodies  composed  ?  Do  we  have  any  direct  knowledge  of  these  atoms  ?— 
8.  What  are  rinyk  bodies  f 


INTRODUCTION.  15 

posed  of  only  one  kind  of  particles,  as  carbon,  sulphur,  copper, 
and  gold ;  compound  substances  are  composed  of  two  or  more  kinds 
of  particles,  which  are  held  in  union  more  or  less  intimate  by 
their  affinity.  The  separation  of  the  elements  of  a  compound  is 
called  its  decomposition. 

The  composition  of  a  body  may  be  determined  in  two  ways,  analyti- 
cally or  synthetically.  By  analysis,  the  elements  of  a  compound  are 
separated  from  one  another,  as  when  water  is  resolved  by  the  agency 
of  galvanism  into  oxygen  and  hydrogen ;  by  synthesis  they  are  made  to 
combine,  as  when  oxygen  and  hydrogen  unite  by  the  electric  spark,  and 
generate  a  portion  of  water.  Each  of  these  kinds  of  proof  is  satis- 
factory ;  but  when  they  are  conjoined — when  we  first  resolve  a  particle 
of  water  into  its  elements,  and  then  reproduce  it  by  causing  them  to 
unite — the  evidence  is  in  the  highest  degree  conclusive. 

9.  Matter  is  Indestructible;  that  is,  it  cannot  be  made  to 
cease  to  exist.     This  statement  seems  at  first  view  contrary  to  fact. 
"Water  and  other  volatile  substances  are  dissipated  by  heat;  and 
coals  and'  wood  are  consumed  in  the  fire,  and  disappear.     But  in 
these  and  other  similar  phenomena,  not  a  particle  of  matter  is 
annihilated  :  the  apparent  destruction  is  owing  merely  to  a  change 
of  form  or  of  composition.     The  power  of  the  chemist  is;  therefore, 
limited  to  the  production  of  these  changes. 

10.  Different  Forms  of  Matter. — Matter  exists  in  three  forms 
or  states :  the  solid,  liquid,  and  gaseous.     Besides  these,  there  are 
the   three   imponderable    agents,    Heat,    Light,  and   Electricity, 
which,  if  they  are  ever  proved  to  be  material,  will  constitute  a 
fourth  form  of  matter. 

It  is  believed  that  the  particles  of  a  substance,  even  the  most  solid, 
are  never  in  actual  contact,  but  are  held  in  close  proximity  by  the  two 
opposite  forces  of  attraction  and  repulsion  ;  and  that  the  particular  state, 
whether  solid,  liquid,  or  gaseous,  in  which  a  body  is  seen,  depends  upon 
the  relative  intensity,  for  the  time,  of  these  forces. 

If  the  force  of  attraction  altogether  preponderates  in  a  body,  it 
is  solid,  and  the  particles,  in  general,  are  held  firmly  in  their 

QUESTIONS. — What  are  compound  bodies?  Give  an  illustration.  In 
what  two  modes  may  the  composition  of  a  body  be  determined  ?  Ex- 
plain analysis  and  synthesis. — 9.  Can  matter  be  destroyed  ?  To  what 
is  the  power  of  the  chemist  limited  ? — 10.  What  different  forms  of  matter 
are  there?  What  is  said  of  the  imponderable  agents?  .Are  the  parti- 
cles of  matter  ever  in  contact  ?  Upon  what  will  the  state  of  matter  in 
any  particular  case  depend  ?  Are  not  the  particles  of  solids  in  contact ' 
What  reasons  arc  given  for  this  opinion  ? 


16  INTRODUCTION. 

places,  and  are  incapable  of  motion  among  themselves.  But  the 
particles  are  not  in  actual  contact,  for,  by  cooling,  or  by  great 
pressure,  the  dimensions  of  any  body  may  be  contracted,  and, 
therefore,  its  particles  brought  nearer  to  each  other.  This  will 
appear  more  fully  hereafter. 

In  liquids,  there  is  a  degree  of  cohesion  among  the  particles 
which,  however,  are  capable  of  perfectly  free  motion  among  them 
selves.  That  there  is  a  degree  of  cohesion  existing  between  the 
particles  is  shown  by  the  drop,  which  is  composed  of  particles  held 
together  by  a  slight  force ;  but  this  slight  force  does  not  interfere 
with  the  freedom  of  their  movements. 

Gases  are  distinguished  by  their  tendency  to  expand,  or  enlarge 
their  volume,  when  external  pressure  is  removed.  In  them  cohe- 
sion is  entirely  wanting.  The  term  fluid  is  applied  to  both 
liquids  and  gases. 

Some  substances  are  found  naturally  existing  in  one  of  these  states, 
and  some  in  "another;  and  many  can  be  made  to  pass  from  one  state  or 
form  to  another,  simply  by  varying  their  temperature,  or  the  pressure 
to  which  they  are  exposed.  Thus,  water  at  a  moderate  temperature  is 
liquid,  but  in  the  cold  weather  of  winter  it  freezes,  that  is,  becomes 
solid ;  and  if  it  be  heated  sufficiently,  it  is  changed  into  steam,  or 
becomes  gaseous.  The  metal,  platinum,  is  found  always  in  the  solid 
state,  though  it  may  be  melted  by  very  great  heat;  but  carbon  is  known 
only  as  a  solid.  Several  substances,  found  naturally  in  the  gaseous  state, 
may  be  changed  to  liquids  by  great  pressure,  or  by  extreme  cold ;  and, 
by  a  still  greater  cold,  some  of  them  may  be  frozen.  Others,  as  atmo- 
spheric air,  have  hitherto  resisted  all  attempts  to  reduce  them  to  the 
liquid  or  solid  form. 

Heat,  light,  and  electricity  are  said  to  be  imponderable,  because  they 
possess  no  appreciable  weight ;  but  they  certainly  exhibit  some  of  the 
ordinary  properties  of  matter.  They  may  be  accumulated  in  bodies,  are 
capable  of  being  attracted  and  repelled,  and  often  produce  various  che- 
mical and  mechanical  effects.  But  because  they  possess  no  weight,  so 
far  as  we  can  determine,  many  choose  to  consider  them,  not  as  matter, 
but  only  properties  of  matter. 

QUESTIONS.  —  Is  there  any  cohesion  among  the  particles  of  liquids? 
How  is  this  shown?  How  are  gases  distinguished?  How  is  the  word 
fluid  used  ?  What  is  said  of  the  natural  state  of  substances  ?  What  are 
the  imponderables  ?  Why  are  they  so  called  ? 


I.  HEAT. 

NATURE  AND  SOURCES  OF  HEAT. 

11.  The  word  Heat  is  used  indiscriminately  to  indicate  the  sen- 
sation we  experience  by  placing  the  hand  in  contact  with  a  heated 
body,  or  the  cause  of  the  sensation.     To  indicate  the  latter,  the 
word  caloric  has  sometimes  been  used. 

The  discussion  of  this  subject  properly  pertains  to  Physics,  or  Nafural 
Philosophy,  (6,)  but  the  agency  of  heat  is  so  intimately  connected  with 
nearly  all  chemical  changes,  that  a  treatise  upon  Chemistry  would  be  im- 
perfect without  a  previous  development  of  some  of  its  more  important 
laws  and  phenomena. 

12.  Nature  of  Heat,  —  Heat  cannot  be  obtained  separate  from 
matter ;   it  is  invisible,  and,  so  far  as  we  are  able  to  determine, 
entirely  destitute  of  weight.     It  is  not,  therefore,  (10,)  believed 
to  be  material;   but  in  describing  its  effects,  and  its  relations  to 
matter  in  general,  we  speak  of  it  as  an  exceedingly  subtile  fluid, 
the  particles  of  which  constantly  repel  each  other,  but  are  attracted 
by  other  substances  —  as  capable  of  being  transmitted  through 
space,  and  the  interior  of  bodies,  and  of  being  accumulated  in 
quantities  in   them.     It  is  present  in  all  bodies,  and  cannot  be 
wholly  separated  from  them.     For  if  a  substance,  however  cold, 
be  transferred  into  an  atmosphere  which  is  still  colder,  a  thermo- 
meter placed  in  the  body  will  indicate  the  escape  of  heat. 

Heat  appears  to  be  attracted  by  all  bodies,  but  is  self-repellent,  as  is 
shown  by  the  fact  that  two  bodies  easily  movable,  when  heated  in  a 
vacuum,  repel  each  other. 

13.  Sources  of  Heat. — The  chief  sources  of  heat  are  :  the  Sun, 
Combustion,  and  other  chemical  changes,  Friction,  Electricity,  and 
Vital  Action. 

The  Sun  is  the  great  source  of  heat  to  our  system.  The  inten- 
sity of  the  solar  heat  appears  to  be  directly  in  proportion  to  the 
number  "of  rays  that  can  be  collected  upon  a  given  surface  ;  and 
at  one  time  philosophers  were  able  to  produce  a  greater  hoat  by 

QUKSTIONS.  — 11.  How  is  the  word  Heat  used?  Caloric?  Is  the 
agency  of  heat  connected  with  chemical  changes? -^12.  Can  heat  be 
obtained  separate  from  matter?  Do  we  speak  of  heat  as  being  material  ? 
Is  heat  present  in  all  bodies?  Is  it  attracted  by  matter?  — 13.  What 
sources  of  heat  are  mentioned  ?  How  may  the  sun's  rays  be  concentrated 
so  as  to  produce  a  great  heat? 

2*  (17) 


15        NATURE  AND  SOURCES  OP  HEAl. 

collecting  the  sun's  rays  by  means  of  the  convex  lens  or  conca? 
mirror,  than  by  any  other  mode. 

But  although  the  sun's  rays  are  not  made  use  of  in  the  arts  -when 
great  heat  is  required,  yet  their  momentous  importance  to  all  the  inha- 
bitants of  the  earth  cannot  be  over-estimated.  Without  them  all  the  water 
upon  the  face  of  the  globe  would  soon  be  congealed,  and  animal  and  vege 
table  life  cease  to  exist. 

Combustion  is  the  great  source  of  artificial  heat,  as  the  sun  i.. 
the  source  of  natural  heat.  Besides  wood,  nature  has  provided 
immense  deposits  of  combustible  material,  in  the  form  of  mineral 
coal,  in  the  bosom  of  the  earth.  These  are  found  in  almost  every 
country,  and  seem  to  be  provided  by  the  Creator  as  an  unfailing 
resource  for  man,  when,  from  the  increase  of  the  species,  or  from 
his  own  negligence  or  extravagance,  the  supply  from  the  vegetable 
world  should  fail  or  become  deficient. 

Friction  is  a  well-known  source  of  heat.  By  the  friction  of  the 
parts  of  heavy  machinery,  especially  when  not  well  oiled,  heat  has 
often  been  evolved  sufficient  to  ignite  wood ;  and  the  same  effect  is 
said  to  have  been  produced  in  ships  by  the  rapid  descent  of  the 
cable.  Some  tribes  of  the  aborigines  of  this  country  were  accus- 
tomed to  kindle  their  fires  by  rubbing  smartly  one  piece  of  wood 
against  another.  In  the  boring  of  cannon,  heat  enough  has  been 
evolved  to  raise  the  temperature  of  a  considerable  quantity  of  water 
so  as  to  boil. 

The  heating  effects  of  electricity  will  be  considered  hereafter. 

The  influence  of  vital  action  in  developing  heat  is  seen  in  a"ll 
warm-blooded  animals,  which  are  maintained  at  a  temperature 
often  much  above  that  of  the  air  and  other  surrounding  bodies, 
though  heat  must  constantly  be  escaping  from  them. 

EXPANSION    OF   BODIES    BY   HEAT. — THERMOMETERS. 

14.  All  bodies,  with  a  very  few  exceptions,  expand  when  their 
temperature  is  increased,  and  contract  when  it  is  reduced.  How 
this  effect  is  produced  we  really  do  not  know,  but  appearances  in- 
dicate that  the  particles  of  heat  entering  among  the  particles  of  the 
body,  partially  overcome  their  cohesion,  and  cause  them  to  sepa- 

QUESTIONS. — What  is  the  great  source  of  artificial  heat  ?  What  is  said 
of  friction  as  a  source  of  heat?  — 14.  Are  all  bodies  expanded  by  heat? 
How  are  bodies  affected  by  a  reduction  of  their  temperature  ? 


NATURE  AND  SOURCES  OF  HEAT.        19 

rate  farther  from  each  other.  On  the  other  hand,  when  the 
particles  of  heat  are  withdrawn,  the  molecules  of  the  body  are 
allowed  to  approximate  each  other  more  closely.  A  substance  ia 
therefore  less  dense  when  heated,  than  when  cold. 

15.  Expansion  of  Solids. — The  expansion  of  solids  by  heat  is 
not  very  considerable,  but  may  easily  be  made 

very  sensible.     Let  a  bar  of  brass  be  accurately 
fitted  into  a  gauge,  when  cold,  and  then   let 
it  be  slightly  heated ;  it  will  be  found  to  have 
increased  so  much  in  length  as  not  to  fit  the 
gauge.     If  the  gauge  be  also  made  of  brass, 
and  the  experiment  performed  in  the  warm 
weather  of  summer,  the  same  result  will   be 
produced  by  cooling  the  gauge  in  ice-water, 
because  of  its  contraction  by  the  cold.     This      Expansion  of  SoMs. 
experiment  indicates  a  change  only  in  length,  but  a  corresponding 
change  is  at  the  same  time  produced,  both  in  breadth  and  thick- 
ness, as  may  be  demonstrated  in  various  modes,  which  the  ingenious 
student  will  readily  devise. 

16.  Different    Solids,   when   equally  heated,   do  not  expand 
equally;   every  substance   possesses  an  expansibility'  peculiar  to 
itself.     But  a  body  expanded  by  heat,  and  again  cooled  to  the 
same  temperature  it  had  at  first,  suffers  no  change  in  its  dimensions. 

Nor  does  the  same  substance  expand  equally  at  all  temperatures  with 
an  equal  increase  of  heat ;  in  general,  the  expansibility  increases  with 
the  temperature.  Thus,  a  body  heated  ten  degrees  at  a  high  tempera- 
ture, expands  more  than  wh^n  the  same  amount  of  heat  is  added  at  a 
low  temperature. 

The  different  expansibility  of  the  two  metals,  copper  and  plati- 
num, may  be  shown  by  soldering  together  a  thin  slip  of  each,  and 
applying  a  moderate  heat  to  the  /—  — -^ 

compound  bar.    Both  plates  will  — * 

be  equally  heated,  but  the  cop- 
per being  the  most  expansible, 

the  bar  will  be  Curved,   the  COp-  Different  Expansion  of  two  Metals. 

QUESTIONS. — 15.  How  may  the  expansion  of  a  solid  by  heat  be  shown 
1C.  Do  all  bodies  expand  equally  when  equally  heated?     Does  the  same 
substance  at  different  temperatures  expand  equally  for  equal  increases 
of  temperature  ?     How  may  the  different  expansibilities  of  two  metals, 
as  copper  and  platinum,  be  shown  ? 


•NATURE    AND    SOURCES    OF    HEAT. 


per  being  on  the  convex  side.     See  figure,  in  which  the  copper  is 

supposed  to  be  on  the  lower,  and  the  platinum  on  the  upper  side. 

Other  metals,  used  in  pairs  in  a  similar  manner,  would  show  the 

same  result,  but  with   many  of  them  the  effect  would  be  less 

decided. 

An  instrument  like  the  following,  at  the  same  time  that  it 

shows  the  different  expansibilities  of  two  metals,  serves  as  an 
excellent  thermometer  for  many  practical  pur- 
poses. A  and  B  are  pieces  of  iron  wire  j2(jths 
of  an  inch  in  diameter,  and  a  foot  long;  and 
C  a  piece  of  brass  wire  of  the  same  size  and 
length.  At  the  bottom  they  are  all  fastened 
together  by  brazing  or  otherwise ;  at  the  top,  a 
piece  of  brass  is  fixed  to  the  two  pieces  of  iron, 
and  through  it,  near  the  centre,  is  a  hole  in 
which  the  brass  wire,  C,  plays  freely.  Now, 
by  immersing  the  thin  wires  in  boiling  water, 
hot  oil,  or  melted  lead,  they  are  all  expanded ; 
but  the  brass  expanding  more  than  the  iron, 
its  upper  end  is  pushed  upward  against  the 
lever,  D,  which  in  turn  acts  upon  E,  producing 
considerable  motion  at  its  extremity,  where  may 
be  placed  a  graduated  scale,  as  S.  Such  an 
instrument  will  be  sensibly  effected  by  even 
moderate  changes  of  temperature. 
The  following  table  shows  the  expansion  in  length  of  rods  of 

several   substances,  when   transferred  from   the  freezing  to  the 

boiling  point  of  water : 


Different  Expansion 
of  Metals. 


Substances. 
Flint  frlasfl 

Expansion  in  Frac- 
tion of  Length. 
i 

Substances. 

Expansion  in  Frat 
tion  of  Length. 

Wood 

Brass  

Ji* 

_J__ 

Zinc  

] 

frnld 

1111 
*4ir 

Tin  

33 

Silver 

Bismuth  

¥38 

•Jo  5 

Lead  

1 

Steel 

-5-5V 

Antimony 

I1 

J~ 

" 

QUESTIONS. — Describe  the  instrument  represented  by  the  second  figure 
of  this  paragraph.  What  is  the  design  of  the  instrument?  What  are 
gome  of  the  most  expansible  of  the  metals,  as  indicated  in  the  table  ? 


NATURE    AND     SOURCES    OP    HEAT. 


17.  Practical  Applications. — This  property  of  bodies,  and, 
particularly  of  the  metals,   has  been  applied  to  various  useful 
purposes  in  the  arts.     The  iron  band  or  tire  of  a  carriage-wheel 
is  made  a  little  smaller  than  the  circumference  of  the  wheel,  but, 
being  expanded,  is  sufficiently  enlarged  to  be  slipped  on ;  and  the 
immediate  application  of  water  prevents  it  from  burning  the  wood, 
and  brings  the  iron  to  its  original  dimensions,  causing  it  to  grasp 
the  wheel  with  great  firmness.     Other  examples  are  of  frequent 
occurrence  in  the  arts. 

The  expansions  and  contractions  of  bodies  by  change  of  temperature 
also  occasion  some  inconveniences.  The  accurate  movement  of  clocks 
depends  upon  the  length  of  their  pendulums,  which  being  sensibly  affected 
by  changes  of  temperature,  they  are  made  to  go  faster  in  cold,  and  slower 
in  warm  weather. 

Brittle  substances,  when  unequally  heated,  are  often  broken  by  the 
unequal  expansions  and  contractions  to  which  they  are  liable.  The 
danger  is  greater  if  the  substance  is  a  bad  conductor  of  heat,  as  is  the 
case  with  glass,  and  particularly  if  it  is  thick.  Hence,  glass  vessels  that 
are  to  be  used  about  the  fire,  or  with  hot  water,  should  be  made  as  thin 
as  is  consistent  with  the  requisite  strength. 

Metallic  or  other  instruments  used  for  measuring  length  or  capacity 
vary  with  change  of  temperature — a  circumstance  that  sometimes  occa- 
sions serious  difficulty  where  very  great  accuracy,  of  measurement  is 
required. 

It  has  been  found  by  very  accurate  examination,  that  the  Bunker  Hill 
Monument,  which  is  built  of  granite,  is  daily  made  to  change  its  position 
slightly,  by  the  heat  of  the  sun,  which  expands  the  sides  upon  which  the 
rays  fall. 

18.  Expansion  of  Liquids. — In  solids,  the  expansive  force  oi 
heat  is    opposed  by  the  cohesion  of  their 

particles,  and  is  therefore  less  effective  than 
in  liquids,  in  which  there  is  only  a  very 
slight  cohesion  of  the  particles.  A  liquid, 
therefore,  will  expand  on  being  heated, 
much  more  than  a  solid. 

The  expansion  of  a  liquid  may  be 'shown  in 
the  following  manner.  Take  a  glass  flask  (called 
a  mattrass  or  bolt-head),  of  the  form  represented 
in  the  figure,  and  partly  fill  it  with  some  liquid, 
as  water,  and  tie  a  thread  around  the  stem,  as 
on  A,  to  indicate  the  height  of  the  water  in  it ; 
and  then  apply  for  a  few  minutes  the  heat  of  a 
spirit-lamp. ..  Both  the  glass  and  the  water  will 


Expansion  of  Liquids. 


QUESTIONS. — 17.  What  is  said  of  the  tire  of  wheels  ?  How  are  brittle 
substances  affected  by  sudden  changes  of  temperature?  What  is  said 
of  the  Bunker  Hill  Monument?  18.  What  is  said  of  the  expansion  of 
liquids  by  heat?  How  may  the  expansion  of  a  liquid  be  shown? 


THERMOMETERS. 

be  expanded ;  but  the  water  will  expand  more  than  the  glass,  and  will 

then  rise  in  the  stem,  as  shown  rn  B. 

But  all  liquids  when  equally  heated  do  not  expand  alike,— ^every  one 

possesses  an  expansibility  peculiar  to  itself.     Thus,  it  has  been  found  by 

making  the  experiment,  that  1000  parts  of  water,  at  the  freezing  point, 
when  heated  so  as  to  boil,  are  expanded  to  1046  parts ;  but 
1000  parts  of  mercury,  heated  in  like  manner,  expand  only 
to  1008  parts.  Ether  is  more  expansible  than  alcohol,  an<» 
alcohol  more  expansible  than  water. 

Liquids,  as  well  "as  solids  (16),  are  expanded  more  at  high 
than  at  low  temperatures,  by  a  given  addition  of  heat. 

19,  Expansion  of  Gases. — All  gases  expand  equally 
when  equally  heated,  and  the  expansion  is  proportional 
to  the  increase  of  temperature.  When  100Q  parts  of 
any  gas  are  heated  from  32°  to  212°  of 'Fahrenheit's 
thermometer  (an  instrument  soon  to  be  described),  they' 
expand  to  1365  parts,  or  ^3  part  of  the  volume  at  32° 
for  each  degree. 

In  the  case  of  gases  that  are  capable  of  becoming  liquid  by 
pressure,  this  law  does  not  hold  strictly  true  when  they  are 
about  to  assume  the  liquid  form. 
*Jjpansion        To  ghow  the  expansion  of  air  by  heat,  let  a  glass  flask,  filled 
with  air,  be  placed  as  in  the  figure,  with  its  mouth  immersed 
in  water ;  then  warm  it  slightly,  by  grasping  the  "Wlb  in  the  hands,  or 
breathing  upon  it,  when  the  air  will  escape  in  bubbles,  in  consequence 
of  its  expansion  by  the  heat.     On  cooling,  the  air  within  contracts,  and 
the  water  rises  in  the  stem  to  supply  the  place  of  the  air  which  was 
expelled. 

THERMOMETERS. 

20,  Thermometers  are  instruments  for  ascertaining  and  mea- 
suring changes  of  the  temperature  of  bodies,  of  which  there  are 
several  kinds.  The  name  is  derived  from  the  two  Greek  words, 
therjnos,  heat,  and  metron,  a  measure. 

The  first  instrument  of  the  kind,  so  far  as  we  know,  was  con- 
structed but  little  more  than  two  hundred  and  fifty  years  ago,  by 
Sanctorio,  an  Italian  philosopher. 

Sanctorio' s  thermometer  was  made  in  the  following  manner.  A 
glass  tube  of  small  diameter,  having  a  bulb  blown  at  one  end,  was 

QUESTIONS. — Do  all  liquids  expand  equally  when  equally  heated  ? 
How  much  do  1000  parts  of  water  expand  when  heated  fromjhe  freezing 
to  the  boiling  point?  19.  Do  gases  expand  by  heat?  What  is  the 
amount  of  their  expansion  for  each  degree  of  heat?  How  may  the 
expansion  of  air  by  heat  be  shown?  20.  What  are  thermometers? 


THERMOMETERS.  23 

partly  filled  with  a  colored  liquid,  and  the  stem  passed  through  a 

cork,  and  inverted  in  a  vessel  containing  the  same  kind 

of  liquid,  and  having  a  wide  bottom,  as  in  the  figure, 

so  as  to  stand  upright  firmly.      Through  the  cork  a 

small  perforation  was  made,  so  as  to  allow  the  air  to  pass 

freely,  and  to  the  stem  a  graduated  scale  was  attached, 

to  mark  the  rising  and  falling  of  the  liquid  in  it. 

Now,  in  an  instrument  of  this  kind,  it  is  plain  that 
when  the  bulb  is  heated,  the  air  within  will  be  expanded, 
as  before  explained,  and  the  liquid  in  the  stem  will  fall; 
ind  a  motion  of  the  liquid  in  the  opposite  direction  will 
take  place  when  the  bulb  is  cooled.  The  rise  and  fall 
of  the  liquid  will  also  be  proportional  to  the  change  of 
temperature  in  the  bulb. 

This  thermometer  will  very  well  answer  some  specific 
purposes,  but  as  it  will  be  affected  by  changes  of  atmospheric 
pressure  as  well  as  by  changes  of  temperature,  it  cannot  be  applied 
to  general  use. 

The  differential  thermometer  may  be  con- 
sidered as  a  modification  of  the  preceding. 
It  consists  of  a  glass  tube,  bent  twice  at 
right  angles,  with  a  bulb  at  each  end,  and 
is  supported  on  a  stand,  as  shown  in  the 
figure.  In  the  tube  is  contained  a  portion 
of  colored  oil  of  vitriol,  or  other  liquid ;  but 
both  bulbs  are  left  filled  with  air,  and  to  one 
of  the  arms  is  attached  a  graduated  scale. 
When  both  bulbs  are  equally  heated  or 
cooled,  this  instrument  indicates  no  change  : 
but  if  one  is  heated  or  cooled  more  than  the 
other,  a  motion  is  at  once  occasioned  in  the  liquid  in  the  stem,  the 
direction  of  which  will  be  readily  understood  from  the  explanations 
already  given.  This  thermometer  therefore  indicates  the  difference 
of  temperature  at  any  time  existing  between  the  bulbs,  and  hence 
its  name.  It  is  exceedingly  delicate,  and  is  especially  adapted  for 
Borne  particular  purposes. 


Differential  Thermomter. 


QUESTIONS.  — Describe  Sanctorio's  air  thermometer.     What  objection  ig 
there  to  its  use  ?    Describe  the  differential  thermonwter. 


24  THERMOMETERS. 

'  21.  The  Common  Thermometer, — The  thermometer  in  com- 
mon use  consists  simply  of  a  glass  tube  of  an  exceedingly  small  bore, 
with  a  bulb  blown  at  one  extremity,  and  filled  with  mercury  to  about 
one-third  the  height  of  the  stem.  The  air  being  expelled,  the  tube 
is  hermetically*  sealed,  and  the  freezing  point  ascertained  by  hold- 
ing it  a  short  time  in  water  containing  ice,  and  the  'boiling  point  by 
holding  it  in  the  same  manner  in  boiling  water.  Both  points  are 
marked  on  the  stem  by  a  file.  It  is  necessary  that  these  two 
points  should  be  accurately  determined,  in  order  that  the  indica- 
tions of  different  instruments  may  be  compared  with  each  other. 

By  the  term  freezing  point  here,  is  meant  the  temperature  at  which 
•water  freezes  or  ice  melts,  which,  with  certain  exceptions,  is*  always  the 
same,  as  will  be  fully  explained  hereafter;  BO,  also,  pure  water  always 
boils  at  the  same  temperature,  provided  attention  is  paid  to  certain  cir- 
cumstances to  be  discussed  further  on  in  the  work.  This  temperature  is 
called  its  boiling  point. 

It  will  be  unnecessary  here  to  give  a  minute  description  of  the  method 
of  making  thermometers,  as,  at  the  present  day,  they  can  be  everywhere 
obtained  at  a  very  moderate  price.  "Besides,  the  construction,  though 
simple  in  theory,  is  difficult  in  practice.  It  requires  great  tact  and  dex- 
terity to  produce  one  of  very  moderate  goodness ;  and  without  steadily 
watching  the  process  as  performed  by  another,  or  previously  possessing 
much  practical  knowledge  in  glass-blowing,  &c.,  it  would  be  a  vain 
attempt." — Faraday's  Chemical  Manipulation,  p.  144. 

The  graduation  of  the  scale  of  the  thermometer  is  a  matter  of  great 
importance ;  and  it  would  be  fortunate  for  us  if  we  had  but  one,  instead 
of  three  or  more,  as  is  the  fact.  We  have  seen  that  in  all  thermometers 
there  are  two  fixed  points  ;  and  the  question  now  before  us  is,  into  how 
many  parts  or  degrees,  shall  the  space  between  them  be  divided  ?  Unfor- 
tunately, this  question  has  been  answered  differently  by  different  artists, 
and  in  a  manner  entirely  arbitrary. 

Fahrenheit,  a  German  artist,  whose  thermometer  is  generally  used  in 
this  country  and  in  England,  divided  it  into  180  parts -or  degrees,  and 
placed  the  zero,  or  the  beginning  of  the  scale,  32  degrees  below  the 
freezing  point ;  so  that  the  temperature  of  melting  ice  or  freezing  water 
is  32  degrees,  and  that  of  boiling  water  (32  +  180=)  212  degrees. 

Celsius  of  Sweden  proposed  to  divide  the  space  into  100  parts,  and 
placed  the  zero  at  the  freezing  point.  His  thermometer  is  called  the 
centigrade  thermometer,  and  is  used  in  France  and  Sweden,  and  some 
other  parts  of  Europe. 

*  A  glass  tube  is  sealed  hermetically  by  melting  the  end  by  means  of  the  blow-pipe,  and 
thus  perfectly  closing  it.  For  this  purpose  the  end  is  usually  drawn  out  into  a  fine  point. 

QUESTIONS. — 21.  Describe  the  common  thermometer.  What  are  the 
freezing  and  boiling  points  ?  How  are  these  determined  ?  Describe  the 
scale  adopted  in  Fahrenheit's  thermometer.  Where  is  the  zero  or  begin- 
ning of  this  scale  ?  Describe  the  scale  of  the  centigrade  thermometer. 


THERMOMETERS. 


25 


C. 


Reaumur  divided  it  into  only  80  parts,  placing  the  zero,  or  beginning 
of  the  scale,  like  Celsius,  at  the  freezing  point ;  of  course  the  boiling 
point  is  at  80. 

Below  zero  of  each  of  the  scales,  and  above  the  boiling  point,  degrees 
are  marked,  of  precisely  equal  magnitude  with  those  of  the  other  part  of 
the  scale.  Temperatures  below  zero  are  usually  indicated  by  placing  a 
horizontal  line  before  the  figures  representing  the  degrees.  Thus, 
»- 12°  means  12  degrees  below  zero  on  the  scale  used. 

The  numbers  180,  100,  and  80,  which  severally  represent  the  number 
of  degrees  on  the  above  scales,  are  to  each  other  as  9,  5,  and  4.  Recol- 
lecting, therefore,  that  the  zero  of  Fahrenheit  is  32  degrees  below  that  of 
the  other  scales,  the  expert  arithmetician  will  find  no  difficulty  in  reducing 
the  degrees  of  one  scale  to  those  of  another. 

Thus,  to  convert  the  degree  of  temperature  indicated  by  Fahrenheit's 
scale  into  its  centigrade  equivalent,  we  multiply  the  degrees  above  or 
below  82°  by  5,  and  divide  by  9.  Suppose  the  temperature  by  Faren- 
heit's  thermometer  is  140°,  what  is  the  corresponding  degree  in  the 
centigrade  ?  Ex.  140  —  32  =  108,  and  108  X  5  =  540,  and  540  -f-  9  =  60. 
On  Fahrenheit's  scale,  therefore,  140°  are  equivalent  to  60°  of  the  centi- 
grade thermometer. 

Let  us  suppose  again  that  the  temperature  by  the  centigrade  thermo- 
meter is  60° ;  it  is  required  to  find  the  corresponding  degree  by  Fahren- 
heit's instrument.  Ex.  60X9=540,  and 
540  -7-  5=  108.  To  this  (108)  we  must  now 
add  32,  because  the  beginning  of  Fahren- 
heit's scale  is  32°  below  that  of  the  centi- 
grade. Thus  1 08° -f-  32°=  140°. 

In  this  work,  and  in  most  works  in  the 
English  language,  if  nothing  is  said  to  the 
contrary,  it  is  always  to  be  understood  that 
temperatures  are  expressed  in  degrees  of 
Fahrenheit's  scale ;  but,  to  avoid  confusion, 
we  often  place  F.,  C.,  or  R  ,  after  the  figures 
expressing  the  degrees,  to  indicate  what 
thermometer  has  been  used. 

The  relation  between  the  three  scales 
above  described  is  indicated  in  the  accom- 
panying figure. 

Though  mercury  is  chiefly  used  in  filling 
thermometers,  yet  other  liquids  are  also 
sometimes  employed.  At  very  low  tem- 
peratures mercury  is  frozen,  so  that  it 
ceases  to  answer  the  purpose  designed ;  in  such  cases,  therefore,  alcohol 
thermometers  alone  can  be  used. 

22.  The  Register  Thermometer,  while  it  answers  the  same  pur- 
pose as  another  thermometer,  at  the  same  time  indicates  or  registers 

QUESTIONS. — Describe  the  scale  of  Reaumur's  thermometer.  How  are 
the  degrees  determined  below  the  freezing  point  and  above  the  boiling 
*)oint  ?  How  may  we  convert  temperatures  as  indicated  by  Fahrenheit's 
>,ale  into  its  centigrade  equivalent  ?  How  may  we  convert  centigrade 
,ato  Farenheit  degrees  ?  Is  mercury  always  used  in  constructing  ther- 
mometers ? 

s 


_212 


—  167 


_122 


_77 


—  100 


—  75 


—  50 


—  25 


_80 


—  40 


_20 


Different  Thermometers. 


26 


THERMOMETERS. 


the  extremes  of  temperature  that  may  occur  during  the  absence 
of  the  observer.  It  consists  of  two  thermometers,  with  the  stems 
bent  near  the  bulb,  and  placed  in  a  horizontal  position,  attached 
to  the  same  frame,  as  shown  in  the  following  figure : 


i   i   i    i 


Register  Thermometer. 

The  one  usually  placed  uppermost  is  a  mercurial  thermometer, 
having  in  the  tube  a  small  piece  of  iron  or  steel  wire,  which  is 
pushed  forward  by  the  mercury  as  it  expands,  but  does  not  recede 
•with  it  when  it  contracts.  The  point  at  which  the  iron  is  left,  of 
course  shows  the  maximum  temperature  attained.  The  other 
thermometer  is  filled  with  colored  alcohol,  and  contains  in  the 
liquid  in  the  stem  a  similar  piece  of  iron,  inclosed  in  glass  to  pre- 
vent oxidation,  around  which  the  alco- 
hol flows  while  that  in  the  bulb  is  ex- 
panding, so  as  not  to  be  moved,  but 
which  is  drawn  along  with  it  by  capil- 
lary attraction,  when  it  contracts  so  as 
to  be  kept  at  its  surface.  It  is  there- 
fore left  at  the  lowest  point  to  which 
the  spirit  has  contracted,  and  of  course 
shows  the  minimum  temperature.  Both 
pieces  of  iron  or  steel,  which  thus  serve 
as  indices,  may  be  brought  to  any  posi- 
tion in  their  respective  tubes  by  means 
of  a  magnet  applied  on  the  outside.  j 
23,  Breguet's  Thermometer  is  made 
entirely  of  solids.  It  consists  of  ;A  very 
Breguet's  Thermometer.  thin  strip  of  platinum,  soldered  to  a 


QUESTIONS. — 22.  Describe  the  register  thermometer. 
fitter. 


BregueVs  thermo- 


THERMOMETERS.  27 

similar  strip  of  silver,  and  coiled  in  a  spiral,  as  shown  in  the 
figure  (page  26).  The  upper  end  of  the  coil  is  then  attached  to 
a  firm  support,  and  to  the  other  extremity  is  fixed  a  pointer  or 
index,  which  is  made  to  revolve  by  any  change  of  temperature, 
by  reason  of  the  unequal  expansions  and  contractions  of  the  two 
metals.  Beneath  the  pointer  is  placed  a  circle  which  may  be  gra- 
duated to  any  scale  desired.  It  is  a  very  delicate  instrument. 

A  modification  of  this  instrument  is  used  in  the  United  States'  Coast 
Survey,  for  determining  the  temperature  of  the  water  in  deep  soundings, 
at  sea. 

The  Pyrometer  (from  pur,  fire,  and  metron,  a  measure,)  is  an  instrument 
for  measuring  temperatures  too  high  to  admit  of  the  use  of  the  thermo- 
meter. The  only  one  now  in  use  is  Daniel's  pyrometer,  which  is  not 
of  sufficient  importance  to  require  description  here.  By  it  the  melting 
point  of  cast  iron  has  been  shown  to  be  about  2786°  F.,  that  of  gold 
to  be  about  2016°  F.,  copper  1996°,  silver  I8600,  and  zinc  713a. 

24.  Exceptions  to  the.  general  Law  of  Expansion. — There  is 
a  remarkable  exception  to  the  general  law  (14)  concerning  the 
expansion  of  bodies  by  heat,  as  above  stated.     Water 

is  most  dense  at  the  temperature  of  about  40°,  and 
expands,  whether  it  is  heated  above  this  point  or 
cooled  below  it. 

To  show  this,  fill  an  ounce  vial  with  water  at  a  tempera- 
ture of  65°  or  70°,  and  adapt  to  it  a  cork,  through  which 
passes  a  glass  tube  of  small  bore.  Then  insert  the  cork 
and  tube,  and  fill  the  latter  with  water  one  or  two  inches 
above  the  neck  of  the  vial,  and  expose  the  whole  to  the 
cold  atmosphere  of  winter,  or  immerse  the  vial  in  a  freez- 
ing mixture  of  snow  and  salt ;  the  contraction  of  the  water 
in  the  vial  will  very  soon  be  made  evident  by  the  fall  of 
that  in  the  tube ;  but  the  falling  will  shortly  cease,  arid 
an  x;pward  motion  commence,  indicating  an  expansion  of 
the  Water  in  the  vial,  although  its  temperature  must  be 
all  the  time  falling.  The  volume  of  the  water  has  there- 
fore first  been  diminished  by  reduction  of  its  heat,  and  WaterKxpanrfon 
again  expanded  ;  and  by  making  use  of  the  thermometer,  when  Freezing, 
it  is  found  thatthe  change  takes  place  at  about  39°  or  40°. 

A  large  tnermometer  tube,  nearly  filled  with  water,  may  be  used  for 
the  same  purpose. 

25.  The   most  important  effects  result  from   this  remarkable 
property  of  water.     If  the  density  of  water  continued  to  increase 
until  it  arrived  at  the  freezing  point,  as  is  the  case  with  mercury 

QUESTIONS. — What  is  the  design  of  the  Pyrometer  ?  24.  What  exceptions 
are  there  to  the  general  law  of  expansion  of  bodies  by  heat  ?  Describe 
the  method  of  showing  the  expansion  of  water  by  reduction  of  temperature. 


28 


THERMOMETERS. 


and  other  liquids,  ice  would  be  heavier  than  water,  and  as  soon  as 
formed  would  subside  to  the  bottom  in  successive  flakes,  until  the 
whole  of  the  water,  however  deep,  would  become  solid.  The 
effects  of  such  an  arrangement  can  be  easily  conceived.  Countries 
which,  in  the  present  state  of  things,  are  the  delightful  abodes  of 
innumerable  animated  beings,  would  be  rendered  uninhabitable, 
and  must  inevitably  become  dreary  and  desolate  wastes.  But, 
since  water  expands  previously  to  its  freezing,  as  well  as  during 
this  change,  ice  is  lighter  than  water,  and  floats  upon  its  surface, 
protecting  the  water,  to  some  extent,  from  the  further  influence 
of  frost. 

The  cause  of  the  expansion  of  water  at  the  moment  of  freezing  is  attri- 
buted to  a  new  and  peculiar  arrangement  of  its  particles.  Ice  is  in  reality 
crystallized  water,  and  during  its  formation  the  particles  arrange  them- 
selves in  ranks  and  lines,  which  cross  each  other  at  angles  of  60°  and 
120°,  and  consequently  occupy  more  space  than  when  liquid.  This  may 
be  seen  by  examining  the  surface  of  water  while  freezing,  and  still  better 
by  receiving  particles  of  snow  as  they  fall  upon  a  piece  of  black  cloth. 
They  will  often  be  found  to  be  small  but  beautiful  crystals  or  collections 
of  crystals,  presenting  a  great  variety  of  forms.  Some  of  the  more  com- 
mon forms  are  shown  in  the  figure. 


Snow  Crystals. 


QUESTIONS. — 25.  What  is  said  of  the  importance  of  this  remarkable  pro- 
perty of  water  ?  What  is  suggested  as  the  cause  of  this  expansion  of  watt* 
in  freezing  ? 


DISTRIBUTION     OF     HEAT.  29 

26.  The  view  just  taken  of  the  cause  of  the  expansion  of  water 
when  freezing  is  sustained  by  the  facts  observed  in  the  formation 
of  anchor  ice,  or  ground  ice,  as  it  is  often  called.  This  ice  is 
found  in  certain  circumstances  at  the  bottom  of  bodies  of  water, 
and  not  at  the  top,  as  with  ordinary  ice.  It  has  little  tenacity, 
and  may  be  supposed  to  consist  of  the  primary  crystals  of  water. 
Separately,  they  are  believed  to  possess  a 'higher  specific  gravity 
than  water,  but,  when  aggregated  according  to  the  law  stated 
above,  at  angles  of  60°  and  120°  to  form  common  ice,  on  account 
of  the  insterstices  necessarily  left  among  them,  the  volume  is  so 
increased  as  to  diminish  the  specific  gravity  to  the  point  we  usually 
witness. — Manuseript  Notes  of  Professor  Cleaveland's  lectures  in 
Bowdoin  College,  1832. 


DISTRIBUTION    OF     HEAT. 

Heat  constantly  tends  to  diffuse  itself,  and  its  distribution  is 
effected  by  Conduction,  Convection,  Radiation,  Reflection,  and 
Transmission. 

27,  Conduction  of  Heat. — Heat  is  said  to  be  conducted,  when 
it  is  transmitted  from  particle  to  particle  through  a  body,  as  when 
one  end  of  a  metallic  bar  is  held  in  the  fire  until  the  whole  becomes 
heated. 

The  passage  of  the  heat  in  such  cases  is  evidently  progressive, 
as  may  be  shown  in  the  following  hianner.  Take  a  small  bar  of 
copper,  18  or  20  inches  in  .. 
length,  and  cement  to  it 
several  small  bullets,  or  mar- 
bles, about  two  inches  from 
each  other,  by  means  of  wax, 
as  shvwn  in  the  figure,  and 
then  apply  the  heat  of  a 
lamp  to  one  end.  As  the 

heat    progresses    along    the  Conduction  of  Heat. 

bar,  it  will  melt  the  wax^  and  the  balls  will  drop  off  in  succession, 

QUESTIONS. — 26.  What  is  said  of  anchor  ice  in  this  connection  ?     What 
ave  some  of  the  modes  by  which  heat  tends  to  diffuse  itself?     27.  When 
is  heat  said  to  be  conducted?     How  may  the  conduction  of  heat  along  a 
bar  of  copper  be  shown  ? 
3* 


30  DISTRIBUTION    OF    HEAT. 

the  one  nearest  the  lamp  falling  first,  and  the  one  farthest  from 
it  last. 

Substances  differ  greatly  in  their  power  of  conducting  heat;  a 
rod  of  glass,  or  a  piece  of  charcoal,  an  inch  long,  may  be  heated 
to  redness  at  one  extremity,  and  yet  be  held  in  the  fingers  by  the 
other  extremity;  but  it  cannot  be  done  with  a  similar  piece  of 
metal,  because,  on  account  of  its  better  conducting  power,  th«j 
whole  very  soon  becomes  too  much  heated. 

The  apparent  temperature  of  a  body,  as  determined  by  the  hand, 
will  often  depend  upon  its  conducting  power.  Thus,  if  on  a  cold 
morning  of  winter,  the  hand  is  placed  upon  a  piece  of  metal,  and 
then  upon  a  piece  of  woollen  cloth,  the  former  will  feel  much 
colder  than  the  latter,  because  the  metal  in  equal  times  conveys 
away  from  the  hand  more  heat  than  the  cloth. 

28.  Substances  are  divided  into  two  classes  in  reference  to  their 
ability  to  conduct  heat,  called  conductors  and  non-conductors. 
There  are,  however,  no  absolute  non-conductors;  heat  penetrates 
the  substance  of  all  bodies ;  the  only  difference  in  them,  in  this 

respect,  is  in  the  rapidity  with  which 
the  process  takes  place.  Gold  is  usu- 
ally considered  the  best  conducting 
substance  known;  and  very  porous 
solids,  the  interstices  of  which  are 
filled  with  air,  as  cotton,  or  sheep's 
wool,  and  fur,  are  the  poorest  con- 
ductors. 

A  convenient  method  to  determine 
the  relative  conducting  power  of  dif- 
ferent substances,  is,  to  have  them 
made  into  cylinders  of  equal  diame- 
ter, and  set  in  a  thin  piece  of  wood 

at  sufficient  distances  from  each  other,  both  extremities  of  each 
piece  projecting  a  little  from  the  wood.     If  the  board  be  held  in 

QUESTIONS. — Do  substances  differ  from  each  other  in  their  power  to  con- 
duct heat?  Why  will  some  substances  feel  colder  than  others,  when  it  is 
known  that  all  must  be  at  the  same  temperature  ?  28.  Into  what  two 
classes  are  substances  divided  in  reference  to  their  conducting  powers  ? 
What  is  usually  considered  as  the  best  conductor  known  ?  What  method 
for  determining  the  relative  conducting  power  of  several  substances  is 
pointed  out ! 


DISTRIBUTION    OF    HEAT. 


31 


a  horizontal  position,  a  small  piece  of  phosphorus  may  be  placed 
upon  the  upper  extremity  of  each  of  the  substances  experimented 
upon,  and  the  lower  ends  exposed  to  the  same  temperature  by 
plunging  them  in  heated  oil  or  sand :  and  the  times  that  elapse 
before  the  ignition  of  the  phosphorus  upon  the  several  substances, 
will  indicate  with  some  accuracy  their  relative  conducting  powers. 

The  following  table  exhibits  the  relative  conducting  power  of  several 
metals  and  other  substances  : 

Gold 1000 

Silver 973 

Copper 898 

Platinum 381 

Ion 374 

Zinc 363 


304 

180 

23 

12 

Fine  Clay 11 


Tin 

Lead 

Marble..., 
Porcelain. 


In  the  arts,  advantage  is  taken  of  the  imperfect  conducting  powers  of 
bodies,  to  prevent  the  passage  of  heat  in  any  direction,  particularly  in 
confining  it.  Hence  furnaces  are  generally  lined  with  "  fire-brick,"  or  a 
thick  coating  of  clay  and  sand.  Wooden  handles  are  fitted  to  metallic 
vessels,  or  a  stratum  of  wood  or  ivory  is  interposed  between  the  hot 
vessel  and  the  metal  handle.  Ice-houses  are  constructed  with  double 
walls,  which  have  their  interstices  filled  with  fine  charcoal,  saw-dust,  or 
some  other  non-conducting  substance,  to  prevent  the  influx  of  heat  from 
without. 

The  design  of  clothing  is  to  retain  the  heat  produced 
by  the  system  :  and  hence  the  warmest  clothing  will 
be  that  which  possesses  the  least  conducting  power. 
In  winter,  the  poorest*  conductors  are  selected,  and 
in  summer  the  best,  as  it  is  then  desirable  that  the 
superfluous  heat  maybe  permitted  at  once  to  escape. 
If,  in  summer,  the  temperature  of  the  atmosphere 
should  rise  considerably  above  that  of  the  system, 
it  would  be  found  advantageous  to  use  the  same 
clothing  as  in  cold  weather. 

Snow,  in  consequence  of  its  imperfect  conducting 
power,  serves  as  clothing  to  the  .earth,  and  prevents 
its  surface  from  being  cooled  down  as  low  as  it  would 
otherwise  be. 

Liquids  of  all  kinds,  except  mercury,  are  poor 
conductors  of  heat.  This  may  be  shown  by  ce- 
menting a  thermometer  tube  in  a  glass  funnel, 
inverting  it,  and  filling  it  with  water,  so  as  to 
cover  t-he  bulb  about  a  quarter  of  an  inch,  or 
eve  '^.,as  shown  in  the  figure.  Then  pour  upon  the  surface 


Ether  burns  on  the 
surface  of  Watec. 


Cfe.  -iTiONS. — What  is  the  use  of  "fire-brick"  in  coal-stoves?  How  are 
ice-houses  constructed?  What  is  the  design  of  clothing?  What  is  said 
of  the  benefits  of  snow  in  winter?  How  ia  the  poor  conducting  power 
of  liquids  shown  by  the  burning  of  ether  ? 


82  DISTRIBUTION    OF    HEAT. 

of  the  water  a  little  sulphuric  ether,  aiid  inflame  it;  the  ether 
will  burn  brilliantly,  but  without  affecting  the  thermometer  for 
some  time,  although  the  flame  is  so  very  near  the  bulb. 

In  like  manner,  heated  oil,  poured 
upon  the  surface  of  water  in  a  tum- 
bler, can  scarcely  be  made  to  affect 
a  small  thermometer  placed  at  the 
bottom. 

If  a  tube  ten  or  twelve  inches 
long  be  nearly  filled  with  water  and 
placed  in  an  inclined  position,  so 

Water  boils  in  vessel  with  Ice.          r 

that  the  heat  of  a  spirit-lamp  can 

be  applied  near  the  centre,  the  water  in  the  upper  part  of  the  tube 
may  be  made  to  boil,  while  the, lower  portion  will  remain  per- 
fectly cold.  If,  before  applying  the  heat,  a  piece  of  ice  be  con- 
fined to  the  bottom,  it  will  remain  unmelted  while  the  water  above 
is  boiling.  Mercury,  though  liquid,  is  a  Very  good  conductor 
of  heat. 

Gases  are  even  poorer  conductors  than  liquids  ;  and  it  is  for  this  reason 
that  very  hot  or  very  cold  air  can  be  endured  in  contact  with  a  person, 
though  exposure  to  a  liquid  of  the  same  temperature  would  produce  intense 
pain,  or  perhaps  even  worse  effects.  Double  windows  and  double  doors, 
with  air  between  them,  are  sometimes  used  to  insure  the  greater  warmth 
of  dwellings. 

29.  Convection  of  Heat. — Though  fluids  are  poor  conductors 
of  heat,  yet,  if  the  heat  be  applied  to  the  bottom  of  the  vessel  con- 
taining them,  in  consequence  of  the  mobility  of  their  particles,  it 
is  rapidly  diffused  through  the  whole  mass.  The  heated  portions 
are  expanded,  and  becoming,  in  consequence,  specifically  lighter 
than  the  rest,  they  rise  through  the  centre  of  the  vessel,  the 
colder  portions  around  the  sides  at  the  same  time  descending  to 
take  their  place.  Thus  an  upward  and  a  downward  current  will 
be  at  the  same  time  established,  which  will  continue  until  the 
whole  is  heated  to  the  boiling  point.  This  mode  of  distribution  is 
called  the  convection  of  heat. 

— w 

QUESTIONS. — How  is  the  poor  conducting  power  of  liquids  shown  by 
the  boiling  of  water  in  a  vessel  containing  ice  ?  29.  How  is  the  heat  dis- 
tributed through  a  liquid  when  it  is  applied  to  the  bottom  of  the  vessel 
containing  it  ?  What  name  is  given  to  this  mode  of  the  distribution  of  heat  ? 


DISTRIBUTION    OP    HEAT. 


S3 


These  currents  may  readily  be  shown  by  filling  a  flask  -with  water 
containing  some  insoluble  powder,  as  pulverized  gum  copal,  and  applying 
the  heat  of  a  small  lamp,  as  represented 
in  the  figure. 

When  large  quantities  of.  water  are 
slowly  heated,  the  upper  portions  will 
frequently  be  found  quite  warm;  while 
that  in  the  lower  part  of  the  vessel 
will  remain  comparatively  cold ;  iind  this 
though  the  fire  is  applied  beneath.  Hence 
it  is  not  unfrequent,  in  bathing  establish- 
ments, to  draw  both  warm  and  cold  water 
from  the  same  reservoir. 

Similar  currents  are  produced  in  gasea 
when  heated ;  and  it  is  on  this  account 
that  the  heated  air,  with  the  smoke  and 
other  fjases  from  a  fire,  ascend  in  a  chim- 
ney, or  the  pipe  from  a  stove. 

30.  Radiation  of  Heat, — A  hot 

body  suspended  in  the  air  emits  heat 

in    all   directions    in    right   lines,    like    Currents  formed  in  vessel  oF Water 

radii  drawn  from   tffe  centre  to  the 

surface  of  a  sphere.      This  mode  of  distribution  is  termed  the 

radiation  of  heat. 

The  radiation  of  heat  from  hot  bodies  is  singularly  influenced  by  the 
nature  and  condition  of  their  surfaces,  which  is  perhaps  the  most  important 
circumstance  connected  with  the  subject.  It  is  probable  that  every  sub- 
Stance  in  nature  has  a  radiating  power  peculiar  to  itself,  but,  in  any  case, 
very  much  will  depend  upon  the  nature  of  the  surface  of  the  body.  By 
many  experiments,  it  has  been  proved  that  bodies  with  bright  polished 
surfaces  retain  their  heat  much  longer  than  when  their  surfaces  are 
rough  and  unpolished.  Adding  even  a  thin  coat  of  whiting  or  lampblack 
to  a  bright  tin  vessel  greatly  increases  the  radiating  power  of  its  surface, 
so  that  boiling  water  or  other  hot  liquid  contained  in  it  will  be  cooled- 
more  rapidly  in  consequence.  The  same  effect  will  be  produced  by 
scratching  its  surface  with  coarse  sand-paper. 

Some  important  practical  considerations  will  naturally  suggest  themselves 
in  connection  with  this  subject.  Whenever  it  is  desired  that  the  heat  of  a 
fluid  or  <3ther  substance  should  be  retained,  vessels  with  bright  and  polished 
metallic  surfaces  should  be  used,  but  the  reverse  if  the  heat  is  to  be  distri- 
buted. Thus  tea  and  coffee  pots  are  usually  made  of  some  bright  metal, 
while  stoves  and  stove-pipes,  for  the  diffusion  of  heat,  are  made  with  dark 
and  rough  surfaces.  Pipes  to  convey  steam  from  the  boilers  in  steam- 
engines  to  the  cylinders,  and  pipes  to  convey  heated  air  from  furnaces  to 
the  different  apartments  of  a  building,  should  be  bright,  or  else  they 
should  be  protected  by  some  non-conducting  covering. 


QUESTIONS. — 30.  When  is  heat  said  to  be  radiated?  How  is  the  radia- 
tion of  heat  affected  by  the  nature  of  the  surface  of  the  hentcd  body? 
What  surfaces  radiate  best  ?  What  practical  considerations  suggest 
themselves  in  view  of  these  principles  ? 


34  DISTRIBUTION    OF    HEAT. 

31.  Reflection  of  Heat— That  heat  may  be  reflected,  may  be 
shown  by  standing  at  the  side  of  a  fire  in  such  a  position  that  the 
heat  cannot  reach  the  face  directly,  and  then  placing  a  plate  of 
tinned  iron  opposite  the  grate,  and  at  such  an  inclination  as  per- 
mits the  observer  to  see  in  it  the  reflection  of  the  fire ;  as  soon  as 
it  is  brought  to  this  inclination,  a  distinct  impression  of  heat  will 
be  produced  upon  the  face. 

If  a  line  be  drawn  from  a  radiating  substance  to  the  point  of  a  plane 
surface  by  which  its  rays  are  reflected,  and  a  second  line  from  that  point 
to  the  spot  where  its  heating  power  is  exerted, 
the  angles  which  these  lines  form  with  a  line 
perpendicular  to   the    reflecting   plane    are 
called  the  angles  X)f  incidence  and  reflection, 
and  are  invariably  equal  to  each  other. 
Thus,  let  AB  (see  figure)  be  the  rejecting 

surface,  and  R  a  ray  of  heat,  which  strikes 

A.  D  IB        this  surface  at  D,  in  the  direction  RD;   it 

Reflection  of  Heat.  wil1  be  thrown  off  or  reflected  in  the  direction 

DL     If  a  perpendicular  PD  be  erected  at  tke 

point  D,  the  angle  RDP  will  be  the  angle  of  incidwace,  and  IDP  the  angle 
of  reflection. 

These  principles,  which  have  just  been  developed  concerning  heat, 
apply  as  well  to  the  invisible  rays  emitted  from  a  moderately  heated 
substance,  as  to  those  accompanied  by  light  from  an  incandescent  body, 
or  the  rays  of  the  sun. 

32.  The  Absorption  of  Seat  by  bodies  sustains  an  intimate 
relation  both  to  its  radiation  and  reflection.     Bright,  and  polished* 
surfaces,  it  is  well  known,  are  the  best  reflectors  j   and  these  are 
just  the  ones,  we   have  seen   (30),  which  radiate  least.     And 
rough,  unpolished  surfaces,  which  radiate  heat  best,  are  found  to 
be  the  best  absorbers. 

Surfaces  may  therefore  be  divided  into  two  classes,  those  which 
afford  an  easy  passage  to  heat,  and  those  which  do  not.  The 
former  will  be  good  radiators  and  absorbers,  and  the  latter  good 
reflectors  and  retainers. 

The  color  of  a  body  influences  considerably  its  absorbing,  but  not  it3 
radiating  power;  surfaces  that  are  black,  other  things  being  equal,  absorb- 
ing heat  more  readily  than  those  of  a  lighter  color. 

QUESTIONS. — 31.  How  may  the  reflection  of  heat  be  shown  ?  Define  the 
angles  of  incidence  and  reflection.  Do  these  principles  apply  to  rays  of 
heat  unaccompanied  by  light?  32.  What  surfaces  are  the  best  absorbers 
of  heat?  Into  what  two  classes  may  surfaces  be  divided  in  reference 
to  their  power  to  transmit  heat  ? 


DISTRIBUTION    OF    HEAT. 


35 


Both  the  radiation  and  the  reflection  of  heat  are  well  shown  by  placing 
a  heated  cannon-ball  in  the  focus  of  a  concave  reflector,  having  another 
similar  reflector  facing  it  at  a  distance,  in  the  focus  of  which  is  placed  one 


•    Parabolic  Reflectors. 

of  the  ^ulbs  of  a  differential  thermometer.  The  rays  from  the  ball  C  are 
reflected  in  parallel  lines  from  the  reflector  A  (see  figure),  and  are  again 
concentrated  on  the  thermometer  D,  by  reflection  from  the  second  concave 
mirror  B. 

If  a  piece  of  phosphorus  be  substituted  for  the  thermometer  at  D,  it 
may  often  be  inflamed,  even  when  the  reflectors  are  ten  or  twenty  feet 
distant  from  each  other. 

If  a  lump  of  ice  is  made  use  of,  instead  of  the  heated  ball,  the  thermo- 
meter in  the  focus  of  the  other  reflector  will  fall ;  in  which  case  the  bulb 
of  the  thermometer  is  the  radiating  body,  and  its  heat  is  received  by 
the  ice. 

33,  Transmission  of  Heat, — When  a  ray 
qf  heat  is  thrown^ipon  a  body,  it  must  either 
be  reflected ',  absorbed,  or  transmitted  by  the 
body.  We  have  already  seen  the  conditions 
upon  which  reflection  and  absorption  depend, 
and  it  remains  only  to  consider  the  circum- 
stances of  transmission. 

In  general,  transparent  substances  afford  the 
most  ready  transmission  of  heat,  but  there  is  a 
great  difference  among  them  in  this  respect. 
Even  atmospheric  air  transmits  heat  but  imper- 
fectly. This  is  shown  conclusively  by  an  experi- 
ment of  Daj-y.  He  contrived  to  heat  a  platinum 
wire  by  means  of  galvanism,  within  a  receiver  con- 
taining two  concave  reflectors,  with  a  thermometer 
in  the  focus  of  one  of  them,  the  heated  wire  being 
in  the  focus  of  the  other.  Now,  when  the  air  was 
exhausted  to  f^th  part  of  its  ordinary  density,  the  thermometer,  it  was 

QUESTIONS. — Explain  the  effect  of  parabolic  reflectors  in  reflecting 
heat.  How  is  a  lump  of  ice  to  be  used  instead  of  a  heated  ball  ?  33.  When 
a  ray  of  heat  falls  upon  a  body,  in  what  three  ways  may  it  be  disposed 
of?  How  does  the  presence  of  the  air  affect  the  transmission  of  heat? 


Transmission  of  Heat  in  a 
Vacuum. 


36  RELATION    OF    HEAT 

found,  -would  be  raised,  by  means  of  the  ignited  wire,  three  timw  as 
high  as  when  the  air  in  the  receiver  was  at  its  natural  pressure. 

Bodies  that  transmit  heat  freely  are  said  to  be  diathermanous  (from 
the  two  Greek  words,  dia,  through,  and  thermos,  heat),  as  those  which 
afford  a  free  passage  to  light  are  said  to  be  transparent. 

By  experiments  made  with  a  very  delicate  piece  of  apparatus,  called 
the  thermo-multiplier,  it  has  been  shown  that  the  most  diathermanous  sub- 
stance known  is  rock-salt,  in  pure  transparent  crystals.  Of  different 
specimens  of  glass,  some  are  much  more  diathermanous  than  others, 
though  all  are  equally  transparent ;  and  some  colored  glasses,  and  other 
bodies  only  partially  transparent,  afford  a  ready  passage  to  heat,  or  aro 
highly  diathermanous. 

It  appears,  also,  that  the  ray  of  heat,  like  a  ray  of  light,  is  really  com- 
pound, or  composed  of  rays  of  heat  of  different  kinds,  some  of  which  have 
a  greater  penetrating  power  as  regards  most  diathermanous  media,  than, 
others.  In  this  respect  heat  from  an  oil-lamp  will  differ  from  that  of  a 
spirit-lamp,  though  both  are  equally  intense;  and  the  heat  of  both  will 
differ  from  that  of  heated  metal. 

The  rays  of  heat  from  the  sun  possess  this  penetrating  power,  as  I 
have  called  it,  in  a  greater  degree  than  any  kind  of  artificial  heat.  Thus, 
a  pane  of  window-glass,  held  between  the  face  and  a  coal-fire,  is  found  at 
once  to  intercept  most  of  the  heat ;  but  no  such  effect  is  produced  by 
holding  it  before  the  face  when  exposed  to  the  direct  solar  ray. 

The  rays  of  heat,  like  those  of  light,  may  be^  refracted ;  and  some  of 
them  being  more  refrangible  than  others,  like  the  different  colors  of  light, 
they  may  be  separated  from  each  other  by  means  of  the  prism. 

The  ray  of  heat,  like  a  ray  of  light,  may  also  be  polarized,  and  in  a 
similar  manner.  See  Decomposition  and  Polarization  of  Light. 


RELATION     OF     HEAT    TO     CHANGES     IN     THE 
STATE    OF    BODIES. 

34.  Relation  of  the  Three  Forms  of  Matter  to  each  other.— 
"We  have  seen  above  (10),  that,  omitting  the  imponderable  agents, 
which  are^not  known  to  be  material,  every  substance  must  be  in 
one  of  the  three  forms,  or  states,  solid,  liquid,  or  gaseous;  and 
that  the  particular  form  a  body  assumes  will  depend  upon  the 
relative  intensity  of  the  cohesive  and  repulsive  forces  existing 
among  its  particles. 

If  the  repulsive  force  be  comparatively  feeble,  the  particles  will  adhere 
80  firmly  together,  that  they  cannot  move  freely  upon  one  another,  thus 

QUESTIONS. — What  are  diathermanous  bodies?  Will  heat  from  all 
sources  be  transmitted  alike  ?  What  is  said  of  the  rays  of  the  sun  ii 
this  connection?  May  the  rays  of  heat  be  refracted?  Polarized? 
34.  Upon  what  will  the  particular  form  or  state  of  a  body  depend  ? 


TO    CHANGES    IN    BODIES.  37 

constituting  a  solid.  If  cohesion  is  so  far  counteracted  by  repulsion  that 
the  particles  move  on  each  other  freely,  a  liquid  is  formed  :  and,  should 
the  cohesive  attraction  be  entirely  overcome,  so  that  the  particles  not  oiily 
move  freely  on  each  other,  but  would,  unless  restrained  by  external  pres- 
sure, separate  or  expand  to  an  indefinite  extent,  an  aeriform  substance 
will  be  produced. 

Now,  the  property  of  repulsion  is  manifestly  owing  to  heat ;  and  as  it 
;is  easy,  within  certain  limits,  to  increase  or 'diminish  the  quantity  of  this 
;  principle  in  any  substance,  it  follows  that  the  forms  of  bodies  may  bo 
made  to  vary  at  pleasure :  that  is,  by  heat  sufficiently  intense,  we  have 
reason  to  believe,  every  solid,  provided  decomposition  does  not  take 
place,  may  be  converted  into  a  liquid,  and  every  liquid  into  vapor.  The 
converse  ought  also  to  be  true;  and,  accordingly,  several  of  the  gases 
have  been  condensed  into  liquids  by  means  of  cold,  or  cold  and  pressure 
combined,  and  the  liquids  have  been  solidified.  The  temperature  at 
which  liquefaction  takes  place  is  called  the  melting  point,  or  point  of 
fusion  ;  and  that  at  which  liquids  solidify,  their  freezing  point,  or  point  of 
congelation.  Both  these  points  are  different  for  different  substances, 
but  usually  the  same,  under  similar  circumstances,  in  the  same  body. 

35.  Liquefaction, — By  the  liquefaction  of  a  substance,  we  mean 
its  reduction  from  either  the  solid  or  gaseous  to  the  liquid  state;  but 
generally  it  is  the  former  change  which  is  intended. 

If,  when  the  temperature  of  the  air  is  at  zero,  as  is  often  the 
case  in  some  parts  of  our  country,  a  quantity  of  ice  be  brought 
into  a  room,  and  placed  near  a  fire,  it  will  be  gradually  heated,  like 
any  other  solid,  as  a  thermometer  placed  in  it  will  indicate,  until 
the  temperature  reaches  32° ;  but  it  will  stand  at  this  point  until 
the  whole  is  melted.  The  thermometer  will  then  begin  again  to 
rise,  as  it  did  before.  Now,  it  is  plain  that  it  must  have  been 
receiving  heat  as  rapidly  while  the  thermometer  was  stationary, 
as  before  and  afterwards;  but  the  heat  thus  communicated  did 
not  affect  the  thermometer,  because  it  was  all  absorbed  by  the  ice, 
and  was  expended  in  changing  the  ice  into  water.  It  has  there- 
fore become  insensible  to  the  thermometer,  and  is  properly  called 
latent  heat;  and  if  it  was  known  to  be  material,  we  might  per- 
haps, with  some  propriety,  consider  water  as  a  compound  of  ice 
and  heat. 

The  quantity  of  heat  which  is  thus  lost  or  becomes  insensible, 
during  the  melting  of  a  mass  of  ice,  is  sufficient  to  raise  the  tern- 

QUESTIONS. — To  what  is  the  property  of  repulsion  owing?     What  is 
the  melting  point  of  a  body  ?     The  freezing 'point  ?     35.  What  is  meant  by 
the  liquefaction  of  a  body  ?     Is  heat  always  required  to  produce  lique- 
faction ?     Why  cannot  ice  be  heated  above  32°  ? 
4 


38  RELATIONOPHEAT 

perature  of  an  equal  weight  of  water  about  140°,  as  may  be  shown 
in  the  following  manner :  Let  a  pound  of  water  at  32°  be  mixed 
with  a  pound  of  water  at  172°,  and  the  temperature  of  the  mixture 
will  be  intermediate  between  them,  or  102°.  But  if  a  pound  of 
water  at  172°  be  added  to  a  pound  of  ice  at  32°,  the  ice  will  quickly 
dissolve,  and  on  placing  a 'thermometer  in  the  mixture,  it  will  be 
found  to  stand,  not  at  102°,  but  at  32°.  In  this  experiment,  the 
pound  of  hot  water  which  was  originally  at  172°,  actually  loses 
140°  of  heat,  all  of  which  enters  into  the  ice,  and  causes  its  lique- 
faction, without  affecting  its  temperature. 

36.  Heat  of  Fluidity. — The  heat  thus  required  for  the  lique- 
faction of  solids  is  often  called  their  heat  of  fluidity ;   and  the 
quantity  necessary  for  the  purpose  is  not  the  same  in  any  two 
substances.     While  the  heat  of  fluidity  of  water  is,  as  we  have 
just  seen,  140°,  that  of  spermaceti  is  145°,  that  of  lead  162°,  that 
of  tin  500°,  and  that  of  bismuth  550°.     That  is,  to  melt  any  given 
weight  of  one  of  these  substances,  an  amount  of  heat  is  required  that 
would  heat  the  same  weight  of  the  substance  the  number  of  degrees 
indicated,  provided  no  change  of  state  should  take  place  during 
the  process. 

The  melting  point  of  nearly  all  substances  is  the  same  as  their  freezing 
point ;  but  this  point  varies  greatly  in  different  substances.  Thus,  solid 
mercury  melts  (and  liquid  mercury  freezes)  at  — 39° ;  ice  at  32°  ;  sperma- 
ceti at  132°  ;  sulphur  at  226°  ;  tin  at  442°  ;  lead  at  612°  ;  zinc  at  773°  ; 
silver  at  1873°,  and  gold  at  2016°. 

37.  Freezing  Mixtures  are  made  of  various  salts  and  liquids, 
which  have  such  an  affinity  for  each  other,  that  rapid  liquefaction 
is  produced,  without  the  direct  application  of  heat.     But  as  this 
agent  is  always  required  when  this  change  takes  place,  it  must  be 
absorbed  from  surrounding  objects,  which  therefore  lose  their  heat, 
or  become  cold.     A  good  mixture  of  this  kind  is  made  of  snow,  or 
finely  broken  ice,  and  common  salt,  both  of  which,  when  mixed 
together,  become  rapidly  liquid ;  and  the  process  is  attended  with 
great  cold,  so  that  a  thermometer  immersed  in  it  will  fall  to  zero, 

QUESTIONS. — What  is  the  quantity  of  heat  absorbed  by  ice  when  it  is 
melted?  How  is  this  shown?  36.  What  is  the  heat  of  fluidity  of  a  sub- 
stance ?  Will  it  be  the  same  in  all  substances  ?  What  are  the  melting 
points  of  the  several  substances  mentioned  ?  37.  What  are  freezing 
mixtures  ? 


TO     CHANGES    IN    BODIES.  %9 

or  below.     Of  course,  if  a  vessel  of  water  be  immersed  in  it,  the 
water  will  in  a  short  time  be  frozen. 

Saltpetre,  dissolved  in  cold  spring  water,  will  often  reduce  the  tem- 
perature to  32°,  or  lower,  so  that  water  may  be  frozen  by  it ;  but  the 
greatest  cold  is  produced  in  this  mode  by  mixtures  of  certain  of  the  salts 
and  acids.  Thus,  powdered  sulphate  of  soda  three  parts,  and  diluted 
nitric  acid  two  parts,  mixed  at  50°,  will  sink  the  temperature  to — 3°; 
and  phosphate  of  soda  nine  parts,  and  the  same  diluted  acid  four  parts, 
will  produce  a  cold  of  — 12°.  The  greatest  cold  that  can  be  produced  in 
this  way  is  found  to  be  about — 100°,  but  by  other  means  still  lower  tem- 
peratures have  been  obtained.  But  it  is  not  possible,  in  the  present  state 
of  our  knowledge,  entirely  to  deprive  a  body  of  heat. 

Since  solids,  on  becoming  liquid,  absorb  heat,  as  we  have  seen, 
it  necessarily  follows,  that  when  liquids  become  solid,  heat  must 
be  given  out.  The  freezing  point  of  water  is  usually  said  to  be 
82°;  but  if  it -be  contained  in  a  close  vessel,  and  cooled  very  slowly 
without  agitation,  its  temperature  may  be  reduced,  without  freezing, 
to  20°,  or  lower.  Slight  agitation  will  now  cause  it  to  freeze  sud- 
denly, and  the  temperature  will  rise  at  once  to  32°,  the  ordinary 
freezing  point.  The  portion  that  has  frozen,  therefore,  has  given 
out  sufficient  heat  to  raise  the  temperature  of  the  whole  mass 
gome  12°.  Saturated  solutions  of  several  of  the  salts,  made  at 
elevated  temperatures,  upon  being  slowly  cooled,  exhibit  the  same 
phenomenon. 

A  beautiful  experiment  may  be  performed  by  making  a  satu- 
rated solution  of  Glauber's  salt  in  warm  water,  and  setting  it  aside 
in  a  closely  corked  vial  till  it  cools.  If  now  the  cork  be  removed, 
or  the  vessel  violently  agitated,  the  salt  will  immediately  crystallize, 
and  a  thermometer  placed  in  it  will  rise  several  'degrees. 

38.  Provision  of  Nature. — We  cannot  but  notice  here  the 
beautiful  and  unexpected  manner  by  which  nature,  to  some 
extent  at  least,  checks  the  cold  of  winter,  which  migh£  otherwise 
be  destructive.  The  cold  atmosphere  causes  large  quantities  of 
water  to  cengeal,  but  at  the  same  time  heat  is  given  out,  which 
prevents  so  great  a  reduction  of  temperature  as  might,  but  for 
this  circumstance,  be  experienced. 

QUESTIONS, — What  is  the  greatest  cold  that  can  be  produced  by  freezing 
mixtures  ?  Is  heat  given  out  when  liquids  become  solid  ?  May  water 
have  its  temperature  reduced  below  the  ordinary  freezing  point?  What 
is  the  eifect  on  the  thermometer  when  freezing  at  length  is  produced? 
Describe  the  experiment  with  Glauber's  salt.  38.  How  is  the  excessive 
cold  of  winter1  to  some  extent  checked  ? 


40  RELATION    OP    HEAT 

The  peculiar  mode  provided  by  the  Creator  to  check  the  heat 
of  summer,  which  might  otherwise  become  excessive,  will  be 
noticed  hereafter. 

39.  Vaporization. — By  the  term  vaporization  is  meant  the 
conversion  of  solids  or  liquids  into  gases. 

Aeriform  bodies  are  often  divided  into  vapors  and  gases,  accord- 
ing to  the  relative  force  with  which  they  resist  condensation ;  but 
the  distinction  is  of  little  consequence. 

Heat  is  always  required  to  convert  a  solid  or  liquid  into  a  gas ; 
usually,  it  is  communicated  directly,  as  when  water  is  made  to 
boil  over  a  fire,  but  if  not  applied  directly,  it  will  always  be 
absorbed  from  surrounding  bodies. 

In  most  cases,  when  heat  is  applied  to  solids,  they  first  melt,  or 
become  liquid,  and  afterwards,  by  a  continuance  of  the  heat,  are 
converted  into  vapor;  but  some,  as  metallic  arsenic,  and  certain 
salts,  pass  at  once,  when  heated,  from  the  solid  to  the  gaseous 
state. 

Gases  occupy  considerably  more  space  than  the  liquids  from 
which  they  are  formed.  Water,  when  converted  into  steam, 
expands  about  ]  700  times,  so  that  a  cubic  inch  of  water  forma 
nearly  a  cubic  foot  of  steam ;  but  most  liquids  expand  much  less 
than  this.  Alcohol,  for  instance,  is  expanded,  when  converted 
into  vapor,  only  659  times  its  original  volume,  and  sulphuric 
ether  443  times. 

Volatile  substances  are  such  as  are  readily  converted  into  vapor 
by  heat  or  at  ordinary  temperatures,  while  those  that  are  incapable 
of  this  change  are  often  called  fixed  substances. 

Two  or  more  gases,  whatever  may  be  their  density,  when  brought 
in  contact,  readily  intermix  with  each  other,  and  become  equally 
diffused  through  the  vessel  that  may  contain  them.  This  is  seen 
in  the  atmosphere,  which  is  composed  of  gases  differing  in  density, 
but  they  remain  uniformly  diffused. 

If  -we  fill  two  bottles  with  gases  of  different  densities,  as  hydrogen  and 
carbonic  acid,  and  connect  them  by  a  narrow  tube,  as  shown  in  the  figure 
on  p.  41,  the  lower  containing  the  most  dense  gas,  in  a  short  time  the  two 

QUKSTIONS. — What  is  meant  by  vaporization  ?  Is  heat  always  required 
when  a  vapor  is  formed  ?  Do  gases  occupy  more  space  than  the  solids  or 
liquids  from  which  they  are  formed?  How  many  times  does  water  expnnd 
when  it  takes  the  form  of  steam  ?  Alcohol  ?  Ether  ? 


TO    CHANGES    IN    BODIES. 


41 


gases  will  diffuse  themselves  equally  through  the  whole  space. 
The  mixture  of  the  gases  will  even  take  place  through  thin 
membranes,  whether  animal  or  vegetable  ;  the  least  dense  of 
the  gases  passing  the  most  rapidly. 

A  good  method  to  show  this  is  to  fill  an  ox  bladder  with 
carbonic  acid,  or  even  atmospheric  air,  and  suspend  it  with 
the  neck  tied,  firmly  in  a  large  vessel  filled  with  hydrogen. 
A  transfer  of  the  gases  through  the  substance  of  the  bladder 
will  take  place,  but  the  hydrogen  entering  more  rapidly 
than  the  denser  gas  escapes,  the  bladder  will  after  a  time 
be  burst. 

40.  Ebullition— Boiling  Point. — When  a  liquid  in 
an  open  vessel  is  exposed  to  any  source  of  heat,  the 
temperature  gradually  rises,  like  that  of  any  other  sub- 
stance in  similar  circumstances,  until  a  certain  point    Diffusion  of 

"is  attained,  when  a  violent  motion  commences  in  it, 
called  ebullition  or  boiling;  and  no  heat  can  then  cause  any 
further  increase  of  temperature.  If  the  heat  be  continued,  the 
quantity  of  liquid  gradually  diminishes,  or,  as  we  familiarly  sa,y, 
is  boiled  away,  until  the  whole  is  gone.  The  commotion  in  the 
liquid  is  occasioned  by  portions  of  it  at  the  bottom,  where  the  heat 
is  applied,  being  converted  into  vapor,  and  rising  in  bubbles  to 
the  surface. 

Ordinarily  it  will  be  found  that  water  boils  at  212°,  which  is 
therefore  called  its  boiling  point ;  but  the  tempeMture  at  which 
other  liquids  boil  is  not  necessarily  the  same,  every  liquid  having 
a  boiling  point  peculiar  to  itself.  Thus,  the  boiling  point  of  alco- 
hol is  only  173°,  and  that  of  sulphuric  ether  96°,  while  that  of 
sulphuric  acid  is  620°,  and  that  of  mercury  662°. 

41.  Boiling  Point  dependent  upon  Circumstances. — But  the 
boiling  point  of  a  liquid  is  not  to  be  considered  as  perfectly  con- 
stant; it  depends  upon  several  circumstances,  the  most  important 
of  which  is  the  pressure  of  the  atmosphere  upon  the  surface  of  the 
liquid.    By  heating  a  small  vessel  q£  water  to  about  200°,  and  placing 
it  under  the  receiver  of  an  air-pump,  it  begins  to  boil  when  the  air 
is  very  moderately  exhausted.     So,  on  ascending  a  mountain,  by 

QUESTIONS. — What  is  said  of  the  diffusion  of  gases  of  different  densi- 
ties ?  Describe  the  experiment  with  the  ox  bladder.  40.  What  is  ebulli- 
tion or  boiling  ?  What  is  the  effect  of  continuing  the  heat  ?  What  is  the 
boiling  point  of  water  ?  Is  this  point  in  other  liquids  the  same  ?  41.  What 
are  the  circumstances  which  affect  the  boiling  point  of  a  liquid  ?  Describe 
the  experiment  with  the  air-pump. 
4* 


42  RELATION    OF    II  EAT 

which  a  part  of  the  atmospheric  pressure  is  avoided,  the  boiling 
point  falls  in  proportion  to  the  ascent.  At  the  hospital  of  St. 
Bernard,  situated  upon  a  point  on  the  Alps,  about  8400  feet  above 
the  sea,  water  boils  at  196° ;  and  on  the  top  of  Mount  Blanc  it 
was  observed  by  Sausure  to  boil  at  184°. 

This  is  just  as  we  should  expect,  for  the  expansion  of  the  vapoi 
has  to  take  place  directly  against  the  pressure  of  the  atmosphere, 
on  the  surface  of  the  liquid;  and  the  degree  of  heat  necessary  tx 
produce  the  expansion  will  be  to  some  extent  proportional  to  th 
expansive  force  required. 

The  pressure  of  the  atmosphere  at  the  surface  of  the  sea  is 
usually  about  15  pounds  to  each  square  inch,  but  it  is  subject  to 
some  variation  j  and  the  boiling  point  of  any  liquid  will  of  course 
vary  at  the  same  time  with  the  atmospheric  pressure. 

In  a  perfect  vacuum,  water  boils  at  72°,  and 
sulphuric  ether  at  — 46°,  or  about  140°  lower 
than  in  the  open  air. 

,  As  migjpt  be  expected,  sulphuric  ether  may 
easily  be  made  to  boil  under  an  exhausted  re- 
ceiver, without  heat,  even  in  the  coldest  weather. 
For  this  purpose  let  a  little  good  ether,  in  a  wine- 
glass, be  placed  under  an  air-pump  receiver,  as 
represented  in  the  figure ;  upon  working  the 
pump,  it  will  boil  violently.  The  experiment 

Boiling  of  Ether.      r        ri  .          ..J  ..    r. 

will  usually  succeed  best  if  some  small  pieces  of 
metal  are  dropped  into  the  ether,  before  placing  it  under  the 
receiver. 

While  the  boiling  is  in  progress  considerable  reduction  of  tem- 
perature takes  place,  and  water  contained  in  a  small  vial  placed 
in  the  ether  will  be  frozen. 

42,  Other  circumstances  affecting  the  boiling  point  are,  the 
nature  of  the  containing  vessel,  and  the  presence  of  soluble  sub- 
stances in  the  liquid.  Thus  water  boils  in  metallic  vessels  at 
212°,  but  in  a  clear  glass  vessel  one  or  two  degrees  more  are 

QUESTIONS. — What  is  said  of  the  boiling  point  upon  high  mountains? 
What  is  the  boiling  point  of  water  in  a  vacuum  ?  Describe  the  experi- 
ment with  ether  under  the  exhausted  receiver  of  the  air-pump  ?  While 
the  ether  boils  how  is  the  thermometer  in  it  affected  ?  42.  What  other 
circumstances  are  mentioned  as  affecting  the  boiling  point  ? 


TO    CHANGES    IN    BODIES 


43 


required;  so  any  substance,  as  a  salt,  held  in  solution  in  the 
water,  causes  a  rise  of  the  boiling  point.  Water  saturated  with 
common  salt  bolls  at  224° ;  saturated  with  saltpetre  at  238°,  and 
with  chloride  of  calcium  at  264°. 

43.  Effect  of  increased  Pressure. — If  water  or  other  liquids 
boil  at  a  lower  temperature  by  diminishing  the  pressure  upon  the 
surface,  so  a  higher  temperature  is  re- 
quired for  this  purpose  when  the  pres- 
sure is  increased,  as  in  a  steam  boiler. 
Water  cannot  be  heated  above  212°  in 
the  open  air,  because  any  additional  heat 
is  expended  in  converting  a  portion  of  it 
into  steam,  which  at  once  makes  its  escape 
into  the  air;  but  if  it  be  confined  in  a 
strong  vessel,  it  may  be  heated  to  any 
temperature  even  to  redness. 

The  rise  of  the  boiling  point  under 
increasing  pressure  is  well  illustrated  and 
proved  by  Marcet's  steam  apparatus, 
which  is  represented  in  the  accompany- 
ing figure.  A  is  a  hollow  brass  globe, 
supported  on  a  stand,  and  in  it  is  con- 
tained a  little  mercury,  and  a  small  quan- 
tity of  water.  Through  an  air-tight  collar, 
a  graduated  glass  tube,  C,  is  inserted,  so 
as  to  reach  very  nearly  to  the  bottom, 
both  ends  of  it  being  open.  B  is  a  ther- 
mometer, having  its  bulb  in  the  water  or 
mercury.  Now,  by  applying  a  lamp  the 
water  is  heated,  and  when  the  tempera- 
ture hag  risen  to  212°,  the  steam  will 
begin  to  issue  freely  through  the  faucet, 
F;  but,  by  closing  the  faucet,  the  escape 
of  the  steam,  will  be  prevented,  and  the 
temperature  witt  rise ;  the  mercury  at  the  same  time  by  the  pres- 
sure of  the  steam  within,  being  forced  up  the  tube  C.  And  the 

^  QUESTIONS.— 43.  Why  cannot  water  be  heated  above  212°  in  the  open 
air  ?    What,  if  the  steam  be  confined  ?    Describe  Marcet's  steam  apparatus. 


Marcet's  Apparatus. 


44  RELATION    OP    *IEAT 

height  to  which  it  may  rise  will  always  show  the  exact  amount  of 
the  pressure. 

By  this  means  it  has  been  determined  that,  at  a  heat  of  250°, 
the  tension  of  steam,  thus  confined  in  a  boiler,  is  equal  to  two 
atmospheres,  or  30  pounds  to  the  square  inch ;  at  275°  its  tension 
is  equal  to  three  atmospheres;  and  four  atmospheres,  or  60  pounds 
to  the  square  inch,  at  294°. 

The  expansive  force  of  steam  confined  in  this  manner  is  the 
propelling  power  in  the  steam  engine.  (See  author's  Nat.  Philo- 
sophy, p.  173.) 

44.  Evaporation.— But  it  is  not  only  when  a  liquid  is  heated, 
and  made  to  boil,  that  it  is  changed  in  to"  vapor;  this  change,  in 
most,  and  probably  in  all  liquids,  and  many  solids,  is  ever  taking 
place,  whatever  may  be  their  temperature,  when  they  are  con- 
tained in  open  vessels.  This  slow  formation  of  vapor  is  termed 
evaporation.  It  is  seen  in  the  drying  of  clothes,  when  wet  with 
water  or  alcohol,  and  in  the  gradual  diminution  of  a  quantity  of 
either  of  these  liquids,  when  left  in  an  open  vessel.  Even  in  the 
forms  of  ice  and  snow  water  gradually  evaporates. 

Evaporation  is  much  more  rapid  in  some  liquids  than  in  others ; 
and  it  is  always  found  that  those  which  have  the  lowest  boiling 
point  evaporate  with  the  greatest  rapidity.  Thus,  alcohol,  which 
boils  at  a  lower  temperature  than  water,  evaporates  also  more 
freely ;  and  ether,  whose  point  of  ebullition  is  yet  lower  than  that 
of  alcohol,  evaporates  with  still  greater  rapidity. 

The  chief  circumstances  that  influence  the  process  of  evapora- 
tion, are  extent  of  surface,  and  the  state  of  the  air  as  to  temperature, 
dryness,  stillness,  and  density. 

The  same  quantity  of  liquid,  exposed  in  a  shallow  vessel,  wil 
evaporate  more  rapidly  than  in  one  of  a  different  form,  because 
of  the  large  amount  of  surface  in  contact  with  the  air;  so,  also 
currents  in  the  air  increase  evaporation  by  removing  the  vapo* 
as  fast  as  it  is  formed.  Increased  pressure  of  the  atmosphere 
diminishes  evaporation. 

QUESTIONS.— What  is  the  tension  of  steam  at  250°  ?  44.  Do  water  and 
other  liquids  take  the  form  of  vapor  without  ebullition  ?  Do  all  liquids 
evaporate  with  the  same  facility?  What  are  the  chief  circumstances 
which  influence  evaporation? 


TO    CHANGES    IN    BODIES.  .45 

45.  Heat  is  absorbed  by  the  Formation  of  Vapor. — During 

the  slow  evaporation  of  water,  or  other  liquids,  as  well  as  when 
they  arc  evaporated  by  boiling,  a  large  amount  of  heat  is  absorbed, 
and  becomes  latent  in  the  vapor  produced.  It  is  on  this  account 
that  ether,  alcohol,  or  even  water,  though  at  the  same  temperature 
as  the  air,  always  feels  cold  when  a  little  is  dropped  upoa  the  hand. 
The  natural  heat  of  the  hand  is  absorbed  and  carried  off  in  the 
vapor  that  is  formed. 

The  evaporation  of  good  sulphuric  ether  may  easily  be  made  to 
freeze  water,  even  in  the  warmest  weather.  For  this  purpose  let  a 
very  small  glass  vial,  covered  with  muslin, 
be  filled  with  water,  and  suspended  by  the 
neck  from  some  convenient  support;  then 
drop  slowly  upon  the  muslin  good  sulphuric 
ether,  from  the  mouth  of  a  vial,  or  by 
means  of  a  dropping  tube.  In  a  few 
minutes,  ice  will  begin  to  form ;  and  if  the 
operation  be  continued,  the  whole  of  the 
water  will  be  frozen,  perhaps  breaking  the 
vial  containing  it. 

Porous  earthen  vessels  are  often  used  in  hotels 
and  other  places,  in  warm  weather,  to  contain 
water  for  drinking.  A  portion  of  the  water 
gradually  exudes  through  the  vessels,  and  eva- 
porates from  the  surface,  by  which  that  within 
is  kept  several  degrees  colder  than  the  tem- 
perature of  the  atmosphere.  Such  vessels  are 
said  to  be  much  used  in  Spain,  where  they  are 
called  alcarrazas.  People  crossing  the  deserts 
of  Arabia  in  caravans,  are  said  sometimes  to  load 
camels  with  earthenware  bottles  filled  with  water,  Freezing  of  Water  byEvapo- 
which  is  kept  cool  by  wrapping  the  jars  with  ration  of  Ether, 

linen  cloths,  and  keeping  them  moist  with  water. 

46.  The  freezing  of  water  by  its  own  evaporation  under  the 
receiver  of  an  air-pump,  is  a  common  experiment.      A  shallow 
dish  containing  strong  oil  of  vitriol  is  first  placed  upon  the  plate 
of  the  machine,  and  over  it,  supported  by  a  tripod  of  wire,  is 
placed  a  small  capsule  filled  with  water.     The  receiver  being  now 
put  in  its  place*  covering  the  whole,  by  working  the  pump  the 

QUESTIONS. — 45.  Is  heat  absorbed  during  the  slow  evaporation  of  & 
liquid?  Describe  the  mode  of  freezing  of  water  by  the  evaporation  of 
ether.  46.  Describe  the  experiment  with  water  and  sulphuric  acid  under 
the  receiver  of  the  air-pump. 


46 


RELATION    OF    HEAT 


Freezing  Water  under  Ex- 
hausted Receiver  with 
Oil  of  Vitriol. 


air  is  exhausted,  rapid  evaporation  from 
the  surface  of  the  water  commences,  which 
is  continued  because  of  the  absorption  of 
the  vapor  by  the  acid  beneath,  until  the 
water  is  frozen.  Without  the  acid,  or 
other  substance  to  produce  the  same  effect, 
the  receiver  would  soon  be  filled  with 
vapor,  and  no  further  evaporation  take 
place;  the  vapor  of  water,  at  ordinary 
temperatures,  not  having  sufficient  tension 
to  lift  the  valves  of  the  pump,  as  it  is 
worked.  Indeed,  a  small  drop  of  water 
may  be  frozen  under  the  receiver  of  an 
air-pump  by  its  own  evaporation,  without 
the  use  of  any  substance  to  absorb  the  vapor.  Let  a  single  drop 
of  water,  on  a  piece  of  charred  cork,  hol- 
lowed a  little  on  its  upper  surface,  be 
placed  under  the  air-pump  receiver,  and 
by  working  the  pump  a  few  seconds,  it 
will  be  frozen  by  the  rapid  evaporation 
which  takes  place  from  its  surface.  The 
burnt  cork  capsule  is  preferable  to  one 
of  glass  or  metal,  since,  as  the  water  does 
not  adhere  to  its  surface,  not  so  much  heat 
is  received  from  it. 

47.  Latent  Heat  of  Vapors. — It  is  not 
easy  to  determine  with  precision  the 
amount  of  latent  heat  in  vapors,  or  the 
relative  quantify  of  heat  absorbed  as  they 
are  formed.  The  results  obtained  by  different  experimenters, 
therefore,  are  not  uniform.  It  is  believed  that  water,  in  taking 
the  form  of  vapor,  absorbs  nearly  1000°  of  heat,  or  heat  enough 
to  raise  the  temperature  of  an  equal  weight  of  water  1000°,  if  it 
could  be  confined.  The  amount  of  heat  in  different  vapors  varies 

QUESTIONS  — What  purpose  docs  the  acid  serve?     Explain  the  method 
of  freezing   a   drop  of  water  upon   a   piece   of  burnt   cork   under  an 
receiver.     47.  What  is  the  amount  of  latent  heat  in  steam  ? 


Freezing  Water  by  its  own 
Evaporation. 


TO    CHANGES    IN    BODIES. 


47 


withlheir  nature;  in  no  two  vapors  is  it  the  same.  Thus,  while 
the  latent  heat  of  watery  vapor  is,  as  we  have  seen,  about  1000°, 
that  of  vapor  of  alcohol  is  only  373°,  that  of  vapor  of  ether  163°, 
vapor  of  oil  of  turpentine  138°,  and  of  sulphide  of  carbon  144°. 
The  heat  which  is  absorbed  when  water  or  other  liquid  is  con- 
verted into  vapor,  wilf,  as  a  matter  of  course,  be  given  out  again 
when  this  vapor  is  condensed  into  the  liquid  form.  On  this  prin- 
ciple, steam  is  often  used  for  warming  buildings,  being  conveyed 
in  pipes  through  the  different  apartments.  As  it  passes  along  the 
pipes,  it  is  condensed,  giving  out  its  heat;  and  the  water  that  is 
formed  runs  back  again  into  the  boiler. 

48,  Distillation, — The  process  of  distillation  consists  simply  in 
evaporating  a  substance,  and  again  condensing  the  vapor,  by 
causing  it  to  come  in  contact  with  a  cold  surface.  This  is  usually 
accomplished  by  having  a  tube  of  considerable  length,  leading 
from  the  top  of  a  close  boiler,  and  passing  in  the  form  of  a  spiral 
through  a  vessel  which  is  kept  filled  with  cold  water. 

In  the  laboratory,  the  apparatus  figured  below  answers  well  for 
distilling  small  quantities  of 
any  liquid.  A  retort,  R,  con- 
tains the  liquid  to  be  distilled, 
and  the  vapor  is  received  into 
a  flask,  F,  the  mouth  of  which 
is  slipped  on  the  neck  of  the 
retort,  but  .the  joint  not  made 
perfectly  air-tight.  The  flask 
should  be  kept  cold  by  being 
immersed  in  cold  water,  or  by 
having  a  small  stream  of 
water  constantly  falling  upon 
it  from  a  vessel  above. 

For  larger  operations,  a  Lei- 
big's  condenser  is  indispensable.  Distillation. 
It  consists  of  a  glass  flask,  for  a 

boiler,  which  may  be  heated  in  a  small  furnace,  as  represented  in  the 
figure  on  page  48,  or  by  means  of  a  spirit-lamp,  and  a  metallic  case,  a,, 
in  which  is  inserted,  through  perforated  corks,  a  glass  tube,  dd,  designed 


QUESTIONS. — Describe  the  mode  of  warming  buildings  by  the  use  of 
steam.     48.  In  what  does  the  process  of  distillation  consist  ? 


48  RELATION    Or     II  EAT 

to  be  kept  constantly  surrounded  with  c'old  water.  From  the  vessel,  i,  o 
stream  of  cold  water  enters  the  funnel,  c,  and,  as  it  is  heated,  escapes  at 
the  highest  part  by  the  tube,  //.,  and  is  collected  in  a  basin,  b.  The  glass 
tube,  dd,  is  connected  at  one  end,  by  means  of  a  smaller  tube,  with  th« 
boiler,  and  at  the  other  end,  with  the  receiving-vessel,  e,  in  which  is  col 


Distillation. 

lected  the  distilled  liquid  condensed  in  passing  through  the  tube,  dd.  The 
crooked  funnel  in  the  boiler  serves  to  introduce  the  liquid  to  be  distilled. 

By  the  process  of  distillation  volatile  substances,  whether  liquid  or 
Bolid,  may  be  separated  from  those  that  are  fixed,  or  even  from  such  as 
are  less  volatile  than  themselves  Water  is  distilled  to  purify  it  from 
salts  or  other  substances  it  may  contain  in  solution  or  suspension ;  and 
alcohol,  by  distillation,  is  separated  from  water,  which  is'  less  volatile 
than  itself,  as  well  as  from  fixed  substances. 

The  application  of  this  process  to  solids  is  usually  termed  their  sub- 
limation. 

49.  Boiling  produced  by  Cold. — We  have  seen  above  (41)  the 
effects  of  diminishing  or  removing  the  atmospheric  pressure  in 
promoting  ebullition,  and  we  are  now  prepared  to  understand 
another  ingenious  method  of  accomplishing  this  object.  Let  a 
flask,  with  a  cork  well  fitted  to  its  mouth,  be  partly  filled  with 
water,  and  made  to  boil  briskly  by  means  of  a  spirit-lamp ;  then 
suddenly  insert  the  cork  and  remove  the  lamp :  the  water  will 

QUESTIONS. — Describe  Leibig's  condenser.  How  is  it  that  substances 
may  be  separated  from  one  another  by  distillation  ?  49.  Describe  the 
experiment  of  boiling  water  by  the  application  of  cold. 


TO    CHANGES     IN     BODIEB. 


49 


Boiling  by  Cold. 


continue  to  boil,  and  by  immersing  it  in  cold 
water,  as  shown  in  the  figure,  the  boiling  will 
become  violent.  The  same  effect  will  be  pro- 
duced by  in-verting  the  flask  and  applying 
snow  or  even  cold  water  to  the  bottom.  But 
if  the  flask  be  held  again  a  moment  over  the 
lamp,  the  boiling  will  instantly  cease.  The 
reason  of  this  is,  because  the  upper  part  of 
the  flask,  when  the  cork  is  inserted,  is  filled 
with  steam,  which  is  condensed  by  the  appli- 
cation of  cold  to  the  outside,  and  a  vacuum 
produced,  The  warm  water  within  then  boils, 
as  in  a  vacuum  produced  by  any  other  means; 
but  if  heat  be  applied,  steam  will  be  again  formed,  and  fill. the 
upper  part  of  the  flask,  and,  by  its  pressure  upon  the  surface  of 
the  water,  prevent  further  boiling. 

If  the  flask  is  firmly  corked,  so  as  to  exclude  the  air  perfectly,  when 
it  has  becom^  cold  the  water  within,  as  the  flask  is  handled,  will  fall  from 
side  to  side,  almost  like  masses  of  ice,  and  producing  a  similar  sound  to 
the  ear.  This  is  because  there  being  no  air  within  to  break  up  the  water 
as  it  is  thrown  in  any  direction,  it  falls  in  a  mass  and  strikes  against  the 
sides  of  the  glass  with  much  the  same  effect  as  a  solid.  A  small  toy  of 
this  kind,  made  of  glass  tube,  and  hermetically  sealed ,  is  called  a  water- 
hammer. 

50,  The  Cryophoms.  —  The  cryophorus,  or 
frost-bearer  (from  the  two  Greek  words,  cruos, 
frost,  and  pTiero,  I  bear),  is  an  instrument  for 
freezing  water  by  its  own  evaporation,  whicb 
beautifully  illustrates  some  of  the  foregoing 
principles.  It  consists  of  a  tube,  half  an  inch 
or  more  in  diameter,  with  a  bulb  blown  at 
each  end,  one  of  them  having  a  small  aper- 
ture, A,  by  which  a  small  quantity  of  water 
is  introduced,  sufficient  only  partly  to  fill  one 
of  the  bulbs.  This  water  is  first  all  collected 


in   the  lower  bulb,   and   the  heat  of  a  lamp     / 

applied,  so  as  to  cause  it  to  boil  briskly;  and     Cryophorus. 

while  the  interior  is  filled  with  steam,  the  aperture  at  A  is  quickly 

QUESTIONS.— What  will  be  the  effect  of  holding  the  flask  over  a  lamp  ? 
What  is  the  effect  if,  when  cold,  the  flask  is  shaken  ?    60,  Describe  the 

cryophorus, 

5 


50  RELATION     OF     II  EAT 

sealed  hermetically,  and  the  lamp  removed.  When  it  has  become 
cold,  the  water  is  passed  to  the  upper  bulb,  as  represented  in  the 
figure  (p.  49),  and  the  instrument  supported  on  a  stand,  with  the 
lower  bulb  in  a  beaker  glass.  All  the  interior  is  now  filled  with 
vapor  of  water,  except  a  part  of  the  upper  bulb,  but  no  evapora- 
tion of  the  water  can  take  place,  because  of  the  presence  of  this 
vapor.  But  by  removing  the  vapor,  which  is  accomplished  by  sur- 
rounding the  lower  bulb  with  a  freezing  mixture  of  salt  and  snow, 
to  condense  it  rapidly,  evaporation  of  the  water  is  produced,  attended 
with  cold  sufficient  to  freeze  the  most  of  it,  even  in  the  warmest 
weather. 

The  pulse-glasS,  as  it  is  called,  is  a  very  similar  instrument,  and  ^ 
is  made  in  the  same  manner,  except 
that  ether  is  used  in  it,  instead  of 
water.  By  grasping  one  of  the  bulbs 
firmly  in  the  hand,  the  vapor,  by  its 
Pulse-glass.  expansion,  will  immediately  force  all 

the  liquid  into  the  other;  and  the 
moment  it  has  all  passed  through  the  stem,  an^  appearance  of  vio- 
lent ebullition  is  produced,  atterded  by  a-  'distinct  sensation  of 
cold  in  the  hand  which  grasps  the  bulb.  This  is  occasioned  by 
the  rapid  evaporation  of  the  film  of  liquid  lining  the  inside  of 
the  bulb. 

51,  Effect  of  Perspiration  upon  the  Animal  System. — The 
effect  of  evaporation  in  withdrawing  heat  is  admirably  illustrated  by 
the  process  of  perspiration.  The  natural  temperature  of  the  human 
body  is  about  98°,  but  when  we  take  active  exercise,  or  are  exposed 
to  a  great  degree  of  heat,  there  is  a  tendency  to  a  rise  of  tempera- 
ture above  that  which  is  conducive  to  health ;  and  the  most 
injurious  effects  would  ensue,  if  they  were  not  prevented  by  the 
rapid  evaporation  which  takes  place  from  all  parts  of  the  surface 
of  the  system. 

Examples  of  the  power  of  the  human  body  to  sustain  great  and 
apparently  even  dangerous  elevations  of  temperature,  are  on  record- 
It  is  well  known  that  individuals  have  voluntarily  exposed  thcm- 

QUESTIONS. — Describe  the  pulse-glass.  51.  What  is  the  effect  of  perspira- 
tion upon  the  animal  system  ?  Will  the  human  body  sustain  high  tern- 
peratures  for  a  time  without  injury? 


TO    CHANGES    IN     BODIES.  51 

selves  for  several  minutes,  in  ovens,  to  temperatures  even  a  hun- 
dred degrees  above  that  of  boiling  water,  without  suffering  any 
injury.  The  very  rapid  perspiration  that  takes  place  in  such  cir- 
cumstances, prevents  the  destructive  elevation  of  temperature  in 
the  system  which  would  otherwise  take  place. 

52.  Temperature  of  the  Seasons  Modified. — The  heat  of  sum- 
mer is  always  greatly  modified  by  the  evaporation  which  take 
place  from  the  sur^ce  of  the  earth,  and  the  stalks  and  leaves  of 
plants  and  trees.     When  a  stalk  of  Indian  corn  (zea  maize),  or 
other  plant,  is  -cut  down  in   midsummer,  or  a  brsfach  removed 
from  a  tree,  the  leaves  soon  begin  to  wither,  because  of  the  eva- 
poration of  the  moisture  in  them.      But  the  evaporation  is  no 
more  rapid  from  them  after  being  cut  than  before,  but  now  the 
supply  of  water  from  'the  earth,  received  by  the  roots,  ceases,  and 
the  withering  we  notice  is  a  necessary  consequence.      We  see 
therefore  that  vegetation  in  warm  weather  is  sending  forth  into 
the  atmosphere  immense  quantities  of  water  by  evaporation,  besides 
that  which  rises  from  the  surface  of  the  earth  itself;  and  as  a  result, 
the  temperature  of  the  atmospheretis  more  or  less  cooled.     In  other 
words,  the  heat  is  thus  prevented  from  becoming  as_  excessive  as  it 
would  be  but  for  this  arrangement. 

•We  have  seen  above  (38)  that  heat  given  out  by  the  freezing 
of  water  in  winter,  prevents  the  low  reduction  of  temperature  that 
would  otherwise  be  .experienced;  and  we  cannot  here  less  admire 
the  wonderful  provision  of  providence,  by  which,  on  the  other 
hand,  the  excessive  heat  of  summer  is,  to  some  extent,  limited. 

53.  Liquids  upon  very  Hot  Surfaces. — Liquids,  as  water,  thrown  upon 
metallic  surfaces,  heated  nearly  to  redness,  instead  of  adhering  to  the 
surface  and  rapidly  evaporating,  will  sometimes  be  seen  to  roll  around  in 
globules,  apparently  'without  touching,  until   at  length  they  gradually 
disappear.     This  is  occasioned  by  an  atmosphere  of  vapor  that  is  formed 
around  the  globules  of  liquid,  by  its  rapid  formation  preventing  the  tem- 
perature from  rising  as  high  as  the  boiling  point,  and  also  by  its  elasti- 
city preventing  the  liquid  from  coming  in  contact  with  the  metallic  plate. 
Alcohol  dropped  upon  the  surface  of.  heated  oil  of  vitriol,  exhibits  a  like 
phenomenon.     This  has  been  called  the  spheroidal  stale  of  liquids. 

QUESTIONS. — 52.  How  is  the  heat  of  summer  modified  ?  Why  does  a 
plant-stalk,  separated  from  its  root,  so  rapidly  wilt  iu  warm  weather  ? 
Is  water  constantly  evaporating  from  the  leaves  and  stalks  of  plants? 
63.  Describe  the  action  of  a  drop  of  water  upon  a  very  hot  surface. 


62  RELATION    OF    HEAT 

54,  Dew. — Dew  is  a  deposit  of  moisture  from  the  atmosphere 
upon  a  cold  surface  in  contact  with  it.     If,  in  the  summer,  a  ves- 
sel is  left  but  a  few  minutes  filled  with  ice-water,  or  even  cold 
spring-water,  dew  soon  collects  upon  it,  and  after  a  time,  the  water 
thus  condensed  trickles  down   the   surface  in  drops.     A  surface 
upon  which  dew  is  seen  to  form  will  always  be  found  colder  than 
the  surrounding  air;   and  the  particular  temperature  at  which  it 
begins  to  form  is  called  the  dew-point.     When  the  air  is  very  dry, 
this  point  will  always  be  considerably  below  the  temperature  of  the 
air  j   but  when  there  is  much  moisture  present  this  will  not  be 
the  case. 

In  fair  weather,  during  the  summer  season,  there  is  usually 
seen,  in  the  morning,  a  copious  deposit  of  dew  upon  the  leaves 
of  plants,  and  upon  other  substances  exposed  to  the  open  air. 
This  is  occasioned  by  the  radiation  of  heat  from  bodies  at  the 
surface  of  the  earth,  which  takes  place  rapidly  during  the  night, 
cooling  them  down  considerably  below  the  temperature  of  the  air. 
Substances,  therefore,  which  radiate  slowly  (30),  as  polished 
metallic  surfaces,  seldom  have  «any  dew  upon  them,  while  good 
radiating  surfaces  near  them  will  be  abundantly  covered  with  it. 

In  cloudy  weather  (without  rain),  there  is  generally  little  dew, 
because  the  heat  radiated  from  the  earth  is  reflected  back  by  the 
clouds ;  and  by  suspending  even  a  small  handkerchief  by  the  four 
corners,  a  few  inches  from  the  earth,  the  deposition  of  dew  on 
substances  under  it  is,  for  the  same  reason,  prevented. 

In  some  warm  countries,  water  is  said  to  be  frozen  during  the 
night  by  the  rapid  radiation  which  takes  place  from  its  surface. 
The  water  for  this  purpose  is  poured  into  shallow  pans,  so  situated 
as  to  receive  as  little  heat  as  possible  from  the  earth. 

55,  Hygrometers. — Hygrometers  are  instruments  for  determin- 
it<$  the  relative  quantity  of  watery  vapor  present  at  any  time  in 
thfe  atmosphere.     Daniel's  hygrometer  (represented  in  the  figure 
on  p.  53)  is  much  in  use.     It  consists  of  a  tube,  A,  with  a  bulb 
at  each  end,  and  is  formed  in  the  same  manner  as  the  cryophorus 


QUESTIONS. — 54.  What  is  dew?  Under  what  circumstances  is  it  de- 
posited? How  do  the  leaves  of  plants  and  other  bodies  at  the  earth's 
surface  become  colder  than  the  air  ?  Why  is  there  usually  little  dew  in 
cloudy  weather  ?  55.  What  are  hygrometers  1 


TO    CHANGES    IN     BODIES. 


Hygrometer. 


(50),  except  that  it  contains  ether  instead 
of  water.  The  tube  is  supported  by  a  stand  j 
and  the  lower  bulb,  which  is  usually  made 
of  colored  glass,  .is  about  half  filled  with  the 
ether,  having  in  it  the  bulb  of  a  very  deli- 
cate thermometer,  with  its  stem  extending 
upward  in  the  tube.  The  other  bulb  is 
empty,  or  contains  only  "the  vapor  of  ether, 
and  is  covered  with  muslin.  To  the  stand 
B  is  attached  a  small  thermometer,  to  -indi- 
cate the  temperature  of  the  air.  By  pour- 
ing a  little  ether  upon  the  muslin,  the  bulb 
is  cooled,  and  the  vapor  of  ether  within 
condensed,  and  a  rapid  evaporation  of  the 
ether  in  the  bulb  produced,  as  in  the  cryo- 
phorus.  This  occasions  a  cooling  of  the  colored  bulb,  and  a 
deposition  of  dew  upon  its  surface,  the  small  thermometer  within 
showing  the  exact  temperature  at  which  the  process  commences, 
which  is  taken  as  the*  dew-point.  Properly,  however,  it  is  the 
difference  between  the  temperature  thus  obtained,  and  the  tem- 
perature of  the  air,  which  shows  the  real  state  of  the  air  as  to 
moisture. 

A  decided  objection  to  the  use  of  this  instrument  is  found  in 
the  fact,  that  it  is  extremely  difficult  to  determine  accurately 
the  moment  when  the  formation  of  dew  upon  the  bulb  actually 
commences.  Its  indications,  therefore,  cannot  always  be  fully 
relied  on. 

The  wet-bulb  thermometer  is  now  mostly  used  to  determine  the 
hygrometric  state  of  the  atmosphere.  Two  thermometers  are 
attached  to  the  same  support,  as  shown  in  the  figure  on  p.  54, 
one  of  them  having  a  piece  of  muslin  wrapped  around  its  bulb, 
which  is  kept  wet  by  a  string  leading  to  it  from  a  small  fountain 
of  water,  attached  also  to  the  support  between  the  thermometers. 
Now,  as  the  evaporation  from  the  muslin  necessarily  reduces  the 
temperature,  this  thermometer  will  always  stand  a  little  lower 
than  the  other,  the  bulb  of  which  is  dry;  and,  moreover,  as  the 


QUESTIONS.  —  Describe   Daniel's  hygrometer, 
thermometer. 

5* 


Describe   the   wet-bulb 


54 


RELATION    OF    HEAT 


rapidity  of  the  evaporation  from  the  muslin  will 
depend  upon  the  dryness  of  the  air,  the  difference 
between  the  readings  of  the  thermometers  will 
indicate  its  true  hygrometric  condition. 

56.  Watery  vapor  exists  in  three  different  states  : 
1.  As  transparent,  invisible  steam,  as  it  rises  from 
boiling  water,  and  before  it  comes  in  contact  with 
the  air;  2.  As  it  appears  partially  condensed,  after 
escaping  into  the  air;  and  3.  As  it  exists  in  the 
atmosphere  at  all  temperatures,  but  invisible  to 
the  eye.  That  steam,  before  coming  in  contact 
with  the  atmosphere,  is  perfectly  transparent  and 
invisible,  is  shown  by  partly  filling  a  glass  vessel 
with  water  and  causing  it  to  boil  rapidly.  The 
steam  within,  above  the  water,  cannot  be  seen 
until  it  escapes  into  the  air,  and  becomes  partially 
condensed,*as  stated  above. 

Clouds  are  collections  of  watery  vapor,  in  this  partially  con- 
densed state,  in  the  upper  regions  of  the  atmosphere,  and  differ 
from  fog  only  in  their  more  elevated  position. 

The  moisture  that  constitutes  clouds,  when  fully  condensed, 
falls  in  rain  upon  the  earth,  or  is  solidified  and  falls  in  beautiful 
crystals  (25),  as  snow.  If  the  drops  of  rain  are  frozen  after  they 
are  formed,  hail  is  produced. 

If  in  warm  weather  a  quantity  of  air  be  forced  into  a  large  glass 
receiver,  so  as  to  produce  a  pressure  of  at  least  two  atmospheres,  a 
slight  mistiness  will  usually  be  seen  within,  occasioned  by  a  partial  con- 
densation of  the  watery  vapor  forced  in  with  the  air.  If  the  process  is 
several  times  repeated,  drops  of  water  may  be  obtained,  forming  a  kind 
of  artificial  rain. 

In  the  manner  stated  above,  all  the  water  upon  the  surface  of  the 
earth  is  subjected  to  a  constant  natural  distillation ;  pure  water,  in  the 
form  of  vapor,  rises  in  the  air  from  the  leaves  of  plants,  from  the  earth, 
and  from  the  surface  of  the  ocean,  rivers,  and  lakes,  to  be  again  diffused, 
in  rain  and  snow,  over  the  earth,  producing  everywhere  vigor  and  life, 
both  in  the  vegetable  and  animal  world. 

57.  Liquefaction  and  Congelation  of  Gases.— By  great  pres- 
sure, or  by  pressure  and  a  low  reduction  of  temperature,  many  of 

QUESTIONS. — 56.  In  what  three  states  does  watery  vapor  exist  ?  What 
mre  clouds  ?  What  is  rain  ?  57.  How  may  many  of  the  gases  be  reduced 
to  the  liquid  state  ? 


TO    CHANGES    IN    BODIES.  55 

the  gases  may  be  reduced  to  the  liquid  state,  and  the  liquids  thus 
formed  solidified  or  frozen.  Indeed,  all  gases  may  be  considered 
as  the  vapors  of  extremely  volatile  liquids.  Some  of  them,  how- 
ever, have  never  yet  been  reduced  to  th0  liquid  state. 

The  usual  method  to  liquefy  a  gas,  is  to  put  the  materials  from 
which  it  is  to  be  formed  into 
a  strong  glass  tube,  bent  in 
the  middle,  as  represented  in 
the  figure,  and  hermetically 

-,.  .,  A        ,v  •  Liquefaction  of  Gases. 

sealing   it.      As  the   gas  is  ^^ 

evolved  the  pressure  of  course  increases,  but  at  length  a  point  is 
attained,  depending  upon  the  temperature  and  the  nature  of  the  gas, 
when  it  begins  to  condense  as  3  liquid,  the  quantity  of  which  is  in- 
creased by  the  further  evolution  of  gas  from  the  materials,  without 
any  increase  of  pressure,  if  the  temperature  is  kept  uniform.  The 
bent  tube  is  particularly  adapted  for  the  liquefaction  of  cyanogen 
gas.  To  form  this  gas,  dry  cyanide  of  mercury  is  used,  a  portion 
of  it  being  placed  in  the  closed  end  of  the  tube,  and  the  other  end 
hermetically  sealed.  Moderate  heat  is  then  applied  to  the  end 
containing  the  cyanide,  the  other  end  being  cooled  by  a  freezing 
mixture  of  snow  and  salt.  As  the  cyanide  is  decomposed  by  the 
heat,  the  cyanogen  first  takes  the  gaseous  form,  but  is  subse- 
quently condensed  by  the  pressure  and  cold,  and  collects  in  the 
empty  end  of  the  tube. 

Of  the  different  gases,  some  require  a  much  greater  pressure 
than  others  to  condense  them  to  the  liquid  state.  At  0°  sulphurous 
acid  gas  becomes  liquid  under  the  ordinary  atmospheric  pressure, 
but  at  32°  it  requires  a  pressure  of  2  atmospheres  to  produce  the 
effect. ,  Carbonic  acid  gas  at  0°  has  a  tension  of  23  atmospheres, 
and  at  32°  a  tension  of  36  atmospheres;  at  higher  temperatures 
the  tension  is  still  more  increased. 

The  liquids  formed  from  the  gases,  in  the  manner  described, 
may  be  frozen  by  the  great  cold  produced  by  their  own  evapora- 
tion, or  by  exposing  them  in  tubes  to  intense  cold.  In  the  former 
case,  the  solids  formed  will  appear  like  snow,  and  in  the  latter,  like 
*lear,  transparent  ice. 

QUESTIONS. — What  is  the  usual  method  to  liquefy  a  gas  '  Do  all  gasei 
require  a  like  pressure  to  reduce  them  to  the  liquid  state  ? 


50 


RELA  TION    OF    HEAT 


M 


58.  For  preparing  small  quantities  of  solid  carbonic  acid,  the 
following  apparatus  answers  well,  and  is  much  less  expensive  than 
such  as  are  usually  purchased  of  the  manufacturers  of  philoso- 
phical instruments.  \ 

The  generator,  A,  is  made  of  a  common  mercury  flask,  having  the  aper- 
ture at  the  neck  a  little  enlarged,  so 
as  to  be  about  an  inch  and  a  quarter 
in  diameter.  A  plug  of  cast-steel,  B, 
is  then  made  of  a  bar  two  inches  at 
least  in  diameter,  and  turned  with  a 
•wide  and  smooth  shoulder  so  as  to  fit 
accurately  upon  a  collar  of  block-tin, 
when  screwed  into  its  place,  as  repre- 
sented in  the  figure.  The  valves, 
which  are  the  most  difficult  part  to 
construct,  on  account  of  the  great 
pressure  that  is  to  be  overcome,  are 
inserted  in  the  plugs,  a  second  one 
of  which,  precisely  like  the  preceding, 
is  made  to  screw,  into  the  receiver,  C. 
Into  the  upper  end  of  each  plug,  a  hole 
an  inch  in  diameter  is  bored  about  one 
inch  deep,  and  terminates  in  a  conical 
point ;  from  which  an  aperture,  a  tenth 
of  an  inch  in  diameter,  is  bored  quite 
through  the  plug.  E  H  is  composed 
of  two  parts,  so  constructed  that  when 
screwed  firmly  into  the  cast-steel  plug,  and  the  part  H  which  terminates 
in  a  conical  point  screwed  down,  all  escape  of  the  gas  from  the  generator 
is  effectually  prevented.  When  the  part  H  is  screwed  upward,  the  escape 
of  the  gas  around  E  is  prevented  by  the  firm  pressure  of  the  shoulder 
of  E  upon  the  washer  I,  and  a  shoulder  upon  the  lower  part*  H,  which 
presses  against  the  bottom  of  E,  and  produces  the  same  effect  with  regard 
to  the  escape  of  the  gas  around  the  thread  of  the  screw  H. 

Instead  of  the  valve  described  above,  the  following  answers  better  for 
the  generator,  as  the  passage  at  the  bottom  of  the  plug  is 
not  liable,  as  in  the  other  construction,  to  be  closed  by  the 
sulphate  of  soda  which  is  formed.  The  part  H- extends 
quite  through  the  plug,  having  at  the  lower  extremity  a  nut, 
P,  attached  firmly  by  a  screw  and  soldered.  Now  when  the 
screw  H  is  turned  upward,  the  thread  on  which  extends 
from  I  downward  about  an  inch,  the  nut  P  perfectly  closes 
the  passage  below,  but  by  turning  the  screw  down,  the 
passage  through  the  plug  is  opened  at  P,  and  closed  at 
I,  allowing  the  gas  to  escape  laterally,  as  in  the  other 
Construction, 

The  receiver,  C,  is  made  of  common  boiler  iron,   and 
should  be  about  two  inches  internal  diameter,  and  of  the 
same  height  as  the  generator,  which  will  make  it  of  the  capacity  of 

QUESTIONS. — 58.  Describe  the  apparatus  for  preparing  solid  carbonic 
acid. 


Solidifying  Carbonip  Acid. 


TO     CHANGES    IN    BODIES.  57 

about  a  pint.  The  tube  L  should  screw  into  the  plug  connected  with  the 
receiver,  having  its  other  extremity  terminate  in  a  conical  point  t'o  fit 
into  a  cavity  prepared  for  it  in  the  other  plug.  By  means  of  the  stirrup- 
screws  M  and  N,  and  the  block  of  wood  0,  the  receiver  may  then  be 
firmly  screwed  in  its  pl^ce ;  and  when  both  the  valves  are  open,  there 
will  be  a  free  passage  between  it  and  the  generator,  but  no  communica- 
tion of  either  with  the  open  air. 

To  make  use  of  this  apparatus,  the  generator  and  receiver  are  separated, 
and  the  plug  B  being  removed,  2£  pounds  of  bicarbonate  of  soda,  made 
into  a  paste  with  the  same  weight  of  water,  are  introduced  into  A,  and 
21 J  ounces  of  strong  sulphuric  acid  are  poured  into  several  copper  ves- 
sels, made  a  little  shorter  than  the  length  internally  of  tfce  generator,  arid 
of  such  a  diameter  that  they  will  just  pass  the  aperture.  These  being 
nearly  filled  with  acid  are  dropped  into  the  generator,  which,  after  the 
plug  B  is  inserted,  is  allowed  to  lie  on  one  side  for  fifteen  or  twenty 
minutes,  and  several  times  rolled  over,  to  mix  the  acid  with  the  soda. 
The  receiver  is  then  attached  to  it  as  seen  in  the  figure,  by  means  of  the 
stirrup-screws  M  and  N ;  and,  if  kept  sufficiently  cool  by  means  of  ice, 
the  liquid  carbonic  acid  formed  in  A  will  shortly  be  distilled  over  into  C, 
the  passage  between  them  being  of  course  previously  opened. 

The  valves  are  now  to  be  closed,  and  the  receiver,  which  contains  the 
liquid  carbonic  acid,  separated  from  the  generator.  A  small  tin  cup  (not 
represented  in  the  figure)  is  then  to  be  attached  to  the  tube  L,  to  receive 
the  jet  of  acid  from  the  receiver.  It  is  essential  that  the  liquid  acid  should 
escape  into  this  cup,  which  is  effected  by  having  a  small  tube  pass  from 
the  steel  plug  nearly  to  the  bottom  of  the  receiver,  or  by  inverting  the 
receiver  before  opening  the  valve. 

The  apparatus  should  be  well  tested,  at  least  three  times,  before  run- 
ning any  risk  by  venturing  to  handle  it  while  charged.  This  is  best  done 
by  means  of  a  hydraulic  press  ;  but  the  same  object  may  be  accomplished 
very  effectually  by  standing  the  apparatus  when  charged  in  a  tub  of  water 
heated  to  about  150°,  so  that  when  the  apparatus  and  water  have  attained 
the  same  temperature,  it  shall  not  be  lower  than  130°.  If  a  more  severe 
test  is  desired,  the  water  may  be  made  still  warmer. 

In  constructing  an  apparatus,  care  should  always  be  taken  to  make 
the  receiver  of  not  more  than  one-fifth  the  capacity  of  the  generator. 
•The  quantity  of  materials  used  should  also  be  just  sufficienf  very  nearly 
to  fill  the  generator. 

In  using  this  apparatus,  when  the  liquid  is  received  in  the  cup,  it 
hisses  and  boils  with  the  greatest  violence ;  and  the  cold  produced  by 
the  evaporation  of  a  part  of  it  is  so  great  as  to  freeze  the  rest,  which  is 
retained  in  the  cup  as  a  fine  white  snow.  By  rolling  this  in  balls,  and 
wrapping  it  in  cotton,  it  may  be  kept  some  time ;  but  in  the  open  air  it 
evaporates  rapidly,  and  intense  cold  is  produced,  equal,  it  is  said,  to 
— 148°.  By  moistening  the  solid  with  ether,  and  placing  it  in  an  exhausted 
receiver,  it  is  claimed  that  a  temperature  as  low  as  175°  or  180°  below 
zero  has  been  produced. 

The  solid  does  not  mix  with  water  when  immersed  in  it;  a  ball 
of  it  thrown  upon  the  surface  of  water  floats  about  lightly,  and  at 

QUESTIONS. — How  is  the  freezing  of  the  liquid  accomplished  ?  At 
what  temperature  is  the  solid  formed  ? 


58  SPECIFIC    II  EAT. 

length  a  portion  of  water  in  contact  with  it  is  frozen  by  the  intense 
cold.  With  sulphuric  ether  or  chloroform  it  mixes  readily,  and 
the  pasty  mass  rapidly  evaporates,  producing  intense  cold. 

Mercury  which  congeals  at  about  — 40^  is  readily  frozen  by 
being  kept  a  short  time  in  contact  with  the  solid,  surrounded  by 
some  cotton,  or  by  immersing  it  in  a  mixture  of  the  solid  and 
ether  or  chloroform. 


SPECIFIC     HEAT.  —  CAPACITY     OF     BODIES     FOR 
HE  AT  . 

59.  When  a  body  is  exposed  to  any  source  of  heat,  its  tem- 
perature rises,  and  the  substance  of  heat  is  supposed  to  accumu- 
late in  it;  but  the  same  quantity  of  heat,  imparted  to  different 
bodies,  will  not  raise  their  temperature  alike.  Thus,  if  a  pound 
of  water  and  a  pound  of  mercury,  in  similar  vessels,  and  at  the 
same  temperature,  be  exposed  to  the  same  source  of  heat,  the 
temperature  of  the  mercury  will  rise  about  80°,  while  that  of  the 
water  rises  only  1°.  It  appears,  therefore,  that  it  requires  30 
times  as  much  heat  to  raise  the  temperature  of  water  any  given 
amount,  as  it  does  to  produce  the  same  effect  upon,  mercury. 
This  idea  is  expressed  by  saying  that  the  specific  heats  of  these 
substances  are  as  30  to  1;  or  we  say  (as  some  prefer)  that  the 
capacity  for  heat  of  water  is  to  that  of  mercury  as  30  to  1. 

If,  instead  of  comparing  equal  weights  of  the  two  substances, 
we  take  equal  volumes — as  a  pint  of  each — and  expose  them  to 
the  same  uniform  source  of  heat,  we  shall  find  that  while  the 
water  gains  1°  of  heat,  the  mercury  will  gain  2°,  or  a  little  more. 
To  express  this  relation  we  use  the  term  relative  heat;  and  we 
say  therefore  that  water  has  more  than  twice  the  relative  heat  of 
mercury. 

Other  methods  of  determining  the  specific  heat  of  bodies*  have 
been  devised,  one  or  two  examples  of  which  will  be  given.  If  a 

QUESTIONS. — What  is  said  of  the  solution  of  the  solid  in  chloroform  and 
ether  ?  How  may  mercury  be  frozen  by  use  of  the  solid  acid  ?  59.  Will 
the  same  quantity  of  heat  imparted  to  different  bodies  heat  them  alike? 
If  like  quantities  of  water  and  mercury  are  exposed  to  the  same  source 
of  heat  will  they  in  the  same  time  be  heated  alike? 


SPECIFIC     HEAT.  59 

pound  of  olive-oil  and  a  pound  of  water  be  heated  to  some  given 
temperature,  say  80°,  and  then  placed  in  a  cold  room,  and  the 
number  of  minutes  noted  which  is  required  for  each  to  cool  an 
equal  number  of  degrees,  say  to  50°,  it  will  be  found  that  the  oil 
will  cool  in  less  than  half  the  time  required  by  th*e  Water;  but  as 
both  substances  must  be  supposed  to  lose  equal  quantities  of  heat 
in  equal  times,  it  follows  that  the  water  must  have  contained  more 
than  twice  as  much  as  the  oil ;  or  the  capacity  of  water  for  heat 
is  more  than  twice  that  of  this  oil. 

If  a  piece  of  copper,  of  a  pound  weight,  be  heated  to  300°,  by 
holding  it  a  few  minutes  in  mercury  at  this  temperature,  and  then 
immersed  in  a  pound  of  water  at  50°,  the  copper  wiU  give  out 
heat  to  the  water  until  the  temperature  of  both  will  be  at  72°. 
Now,  the  copper  has  lost  228°  of  heat,  and  the  water  has  acquired 
22°.  The  specific  heat  of  water,  therefore,  is  to  that  of  copper  as 
228  to  22. 

It  is  usual  to  make  water  the  standard  in  comparing  the  specific 
heats  of  bodies,  considering  its  specific  heat  as  1-000;  we  shall 
then  have  the  specific  heat  of  mercury  1'|-g°=-033,  and  that  of 
copper  2aa5=-096. 

No  two  substances  have  the  same  specific  heat,  but  every  sub- 
stance has  a  specific  heat  peculiar  to  itself,  and  which  is  to  be 
considered  as  one  of  its  own  peculiar  properties. 

The  following  table  exhibits  the  specific  heats  of  several  well- 
known  substances : — 


Water 1-000 

Iron 0-114 

Copper 0-096 

Lead 0-031 

Sulphur 0--203 

Phosphorus 0-188 

Diamond 0-119 

Graphite 0202 

Charcoal 0-201 


Gold 0-032 

Silver 0-057 

Alcohol 0-645 

Tin 0-056 

Platinum 0-032 

Zinc 0-095 

Mercury.. ., 0-033 

Oil  of  Turpentine 0-467 

Ether 0-503 


The  specific  heat  of  a  body  depends  to  some  extent  upon  its  tempera* 
ture,  being  greater  as  the  temperature  is  higher. 

Change  of  density  in  a  body  is  usually  attended  by  a  correspond- 
ing change  in  its  specific  heat,  which  is  increased  as  the  density  is 

QUESTIONS. — What  is  the  ratio  of  their  capacities  for  heat,  or  their  specific 
hetts  ?    What  is  taken  as  the  standard  for  the  specific  heat  of  bodies  ? 


60 


NATURE    AND     SOURCES    OF    LIGHT. 


diminished,  and  diminished  as  the  density  is  increased.  This  ia 
seen  in  solids,  as  when  a  piece  of  iron  is  heated  by  hammering, 
which  increases  its  density  and  causes  a  portion  of  its  latent  heat 
to  be  given  out,  thus  raising  its  temperature ;  but  is  best  illus- 
trated by  the  gjases,  the  densities  of  which  are  more  easily  made 
to  vary  at  pleasure.  Thus,  if  we  suddenly  compress  a  portion 
of  a  gas,  its  temperature  is  sensibly  raised;  but,  on  the  other 
hand,  if  we  diminish  its  density,  it  becomes  colder  by  the  absorp- 
tion of  heat  occasioned  by  its  increased  capacity  for  heat.  A 
delicate  thermometer  placed  under  the  receiver  of  an  air-pump 
falls  as  the  air  is  exhausted. 

60.  The  Fire  Syringe  is  an  instrument  by  which 
dry  tinder  or  spunk  may  be  ignited  by  the  heat  pro- 
duced by  the  sudden  compression  of  a  portion  of  at- 
mospheric air.  It  consists  of  a  hollow  cylinder, 
closed  at  one  end,  and  a  solid  piston  fitting  it 
accurately,  and  having  in  its  under  side  a  cavity  to 
receive  the  substance  to  be  ignited.  To  use  it,  the 
tinder  or  spunk  is  put  in  the  place  fitted  for  it,  and 
the  piston  is  then  plunged  forcibly  into  the  cylinder; 
on  removing  it,  the  combustible  substance  will  gene- 
rally be  found  ignited.  If  the  cylinder  is  of  glass, 
a  flash  of  light  will  often  be  seen  when  the  air  is 

Fire  Syringe.      Compressed. 


II.    LIGHT. 

NATURE    AND    SOURCES    OF    LIGHT. 

61,  Nature  of  Light. — Although  innumerable  observations 
and  experiments  have  been  made  upon  light,  yet  it  must  be 
admitted  that  some  doubt  and  obscurity  still  remain  concerning 
its  real  nature.  But,  in  the  absence  of  positive  knowledge,  two 
theories  of  light  have  been  proposed,  by  each  of  which  nearly  all 

QUESTIONS.— How  does  change  of  density  in  a  body  affect  its  specific 
heat?  60.  Describe  the  fire  syringe.  61.  Do  we  understand  fully  the 
real  nature  of  light  ? 


NATURE    AND     SOURCES    OF    L-IGHT.  61 

the  phenomena  attending  it  may  be  satisfactorily  explained ;  and 
it  is  admitted  that  each  is  also  attended  with  its  peculiar  difficulties. 
These  are  called  the  Newtonian,  or  corpuscular,  and  the  undulatory 
theories. 

62.  The  Newtonian  theory  supposes  light  to  be  material,  and 
to  consist  of  inconceivably  minute  particles,  which,  however,  are 
too  subtile  to  exhibit  the  common  properties  of  matter.     These 
particles,  emanating  from  luminous  bodies, -such  as  the  sun,  the 
fixed  stars,  and  incandescent  substances,  and  traveling  with  im- 
mense velocity,  excite  the  sensation  of  light,  it  is  supposed,  by 
passing  bodily  through  the  substance  of  the  eye,  and  striking 
against  the  expanded  nerve   of  vision,  the   retina.     The  whole 
language  of  optics  is  founded  on  this  theory. 

63.  The   undulatory  theory,  or  theory  of  Huygens,  which  is 
now  generally  adopted,  denies  to  light  a  separate  material  exist- 
ence, and  ascribes  its  effects  to  the  vibrations  or  undulations  of  a 
subtile  ethereal  medium,  supposed  to  be  universally  present  in 
nature,  the  pulses  of  which,  in  some  way  excited  by  luminous 
objects,  pass  through  space  and  transparent  bodies,  and  give  rise 
to  vision  by  impressing  the  retina,  in  the  same  way  as  pulsations 
of  air  impress  the  nerve  of  hearing,  to  produce  the  sensation  of 
sound. — (See  Natural  Philosophy,  p.  188.) 

64.  Light  is  not  a  homogeneous  substance,  as  might  be  sup- 
posed, but  the  white  light  of  the  sun  is  made  up  of  rays  of  several 
different  colors,  as  will  be  shown  when  we  come  to  speak  of  its 
decomposition,  or  analysis.     So,  also,  it  is  capable  of  producing 
several  distinct  classes  of  effects,  which  have  been  attributed  to  the 
action  of  distinct  agents;  as  the  colorific  rays,  or  the  rays  which 
produce  the  phenomena  of  color,  the  heating,  rays,  and  the  chemi- 
cal rays,  or  those  which  are  capable  of  producing  chemical  changes. 
Thus  it  is  possible,  by  causing  the  solar  ray  to  pass  through  certain 
substances,  to  separate  the  heat  entirely  from  it;  or  its  illuminating 
power  may  be  destroyed,  and  a  distinct,  invisible  ray  of  heat  be 
obtained.     So,  also,  chemical  effects  may  be  produced  by  rays  which 
seem  to  be  destitute  of  any  heating  or  illuminating  power. 

QUESTIONS. — 62.  Describe  the  Newtonian,  or  corpuscular,  theory  of  light. 
63,  Describe  the  undulatory  theory.  64.  What  colored  rays  are  contained 
in  the  white  light  of  the  sun  ?  What  other  rays  ? 


62  NATURE    AND    SOURCES    OF    LIGHT. 

65,  Sources  of  Light. — The  sun  is  the  great  source  of  light  to 
the  earth,  and  all  things  upon  its  surface.  As  rays  of  heat  always 
accompany  the  light  of  the  sun,  it  is  natural  to  suppose  that  the 
sun  is  an  intensely  heated  mass,  which  is  constantly  throwing  off 
both  light  and  heat  in  every  direction,  like  a  red-hot  cannon-ball 
suspended  in  the  air;  but  this  cannot  be  proved.  At  the  present 
day,  it  is  generally  believed  that  the  body  of  the  sun  is  a  dark, 
opaque  substance,  surrounded  by  luminous  clouds,  unlike  any- 
thing, perhaps,  with  which  we  are  acquainted  upon  the  earth,  but 
which  are  the  real  source  of  the  sun's  rays.  These  clouds  are 
supposed  to  be  of  great  thickness;  but  occasionally  they  break 
away  in  places,  showing  the  body  of  the  sun  beneath  them,  which 
constitute  the  spots  often  seen  upon  his  surface. 

The  great  distance  of  the  sun  from  the  earth— 95,000,000  of 
miles — very  probably  will  ever  prevent  us  from  knowing  more 
with  certainty  of  his  real  nature. 

Artificial  liyJit  is  produced  by  various  modes,  but  chiefly  by 
combustion,  by  the  burning  of  a  lamp  or  candle,  or  a  mass  of 
charcoal;  but  it  may  also  be  produced  by  galvanism, — in  a  man- 
ner.to  be  hereafter  explained, — by  decaying  animal  and  vegetable 
substances,  called  phosphori,  and  by  every  means  which  produce 
great  heat. 

All  bodies  begin  to  emit  light  when  heat  is  accumulated  within 
them  in  great  quantity ;  and  the  appearance  of  glowing  or  shining, 
which  they  then  assume,  is  called  incandescence.  The  tempera- 
ture at  which  solids  in  general  begin  to  shine  in  the  dark,  is 
between  600°  and  700°;  but  they  do  not  appear  luminous  in 
broad  daylight  till  they  are  heated  to  about  1000°.  The  color 
of  incandescent  bodies  varies  with  the  intensity  of  the  heat.  The 
first  degree  of  luminousness  is  an  obscure  red.  As  the  heat  aug- 
ments, the  redness  becomes  more  and  more  vivid,  till  at  last  it 
acquires  a  full  red  glow.  If  the  temperature  still  increase,  the 
character  of  the  glow  changes,  and  by  degrees  it  becomes  white, 
shining  with  increasing  brilliancy  as  the  heat  augments.  Liquids 
and  gases  become  incandescent  when  str6ngjy  heated ;  but  a  very 

QUESTIONS. — 65.  What  is  the  great  source  of  light  to  the  earth  ?  How 
is  artificial  light  produced?  At  what  temperature  do  bodies  begin  to 
emit  light  ? 


NATURE    AND     SOURCES    OF    LIGHT.  OU 

high  temperature  is  required  to  render  a  gas  luminous,  more  than 
is  sufficient  for  heating  a  solid  body  even  to  whiteness.  The  dif- 
ferent kinds  of  flame,  as  that  of  a  wood-fire,  candles,  and  gas-lights, 
are  instances  of  incandescent  gaseous  matter. 

Artificial  lights  differ  greatly  in  color,  some  being  of  a  brilliant 
white,  and  others  being  red,  blue,  yellow,  or  green.  The  chemical 
agency  of  artificial  light  is  in  general  analogous  to  that  from  the 
sun ;  but  in  most  cases  it  is  too  feeble  to  produce  very  decided 
effects. 

66.  Many  substances  have  the  power  of  emitting  a  feeble  light,  unat- 
tended by  sensible  heat,  and  are  called  phosphori  (from  two  Greek  words, 
phos,  light,  and  phero,  I  bear).     Certain  living  animals  also  possess  tho 
same  property,  as  the  glow-worm,  and  the  common  fire-fly.      This  pro- 
perty of  bodies  is  termed  their  phosphorescence. 

Some  phosphori,  as  that  prepared  by  mixing  sulphur  and  oyster-shells, 
und  exposing  the  mixture  for  a  time  to  a  strong  heat,  the  diamond,  fluor- 
spar, &c.,  shine  only  after  having  been  heated,  or  exposed  for  a  few 
moments  to  a  strong  light ;  while  others,  as  moist,  decaying  wood,  and 
decaying  fish,  shine  without  such  preparation,  even  at  ordinary  tem- 
peratures. 

Light  sometimes  appears  during  the  process  of  crystallization.  This 
is  exemplified  by  a  tepid  solution  of  sulphate  of  potassa  in  the  act  of 
crystallizing;  and  it  has  been  likewise  witnessed  under  similar  circum- 
stances in  a  solution  of  fluoride  of  sodium  and  nitrate  of  stroutia.  .  An- 
other instance  of  the  kind  is  afforded  by  the  sublimation  of  benzoic  acid. 
Allied  to  this  phenomenon  is  the  phosphorescence  which  attends  the  sud- 
den conti'action  of  porous  substances.  Thus,  on  decomposing  by  heat 
the  hydrates  of  zirconia,  peroxide  of  iron,  and  green  oxide  of  chromium, 
the  dissipation  of  the  water  is  followed  by  a  sudden  increase  of  density 
suited  to  the  changed  state  of  the  oxide,  and  'a  vivid  glow  appears  at  the 
same  instant.  The  essential  conditions  are  that  a  substance  should  be 
naturally  denser  after  decomposition  than  it  was  previously,  and  that  the 
transition  from  one  mechanical  state  to  the  other  should  be  abrupt. 

67,  Photometers  are  instruments  for  measuring  the  comparative 
intensities  of  different  lights,  of  which  several  kinds  have  been 
proposed;    but  it  does  not   enter  into   our  present  purpose   to 
describe  or  discuss  their  comparative  merits. 

To  determine  the  comparative  intensities  of  two  lights,  as  that 
from  different  candles  or  lamps,  the  following  method,  originally 
proposed  by  Count  Kumford,  is  perhaps  as  reliable  as  any ;  and 
lias  the  advantage  of  requiring  little  and  very  cheap  apparatus. , 
Let  L  be  a  lamp,  and  C  a  candle,  the  lights  of  which  we  desire  to 

QUESTIONS. — Do  artificial  lights  dift'er  in  their  colors?  GO.  What  are 
phosphori  ?  67.  What  are  photometers  ? 


64  NATURE    AND    SOURCES    OP    LIGHT. 

compare.  Provide  a  screen,  S,  of  white  paper,  which  is  to  be  put 
in  a  frame  and  properly  supported  by  a  stand,  as  shown  in  the 
figure,  and  also  a  small  cylinder,  C,  of  wood  or  some  opaque  sub- 
stance. Then  place  this  cylinder  in  an  upright  position  in  front 
of  the  screen,  in  such  a  position  that  its  shadow  from  both  of  the 
lights  shall  be  thrown  side  by  side  upon  the  screen,  but  not  over- 
lapping-each  other,  and  removing  the  lights  to  different  distances, 
until  the  shadows  appear  of  perfectly  equal  intensities.  The  com- 
parative intensities  of  the  two  lights  will  then  be  as  the  squares 
of  the  distances  of  the  lights  from  the  screen.  In  the  present 
case,  17  will  be  the  shadow  from  the  light  of  the  lamp,  and  C' 
that  from  the  light  of  the  candle ;  and  the  intensity  of  the  lamp 
light  will  be  to  that  of  the  candle  light  as  LL'2is  to  CO'2.  If  LL' 


Photometer. 

is  50  inches  and  CC'  45  inches,  then  will  the  light  of  the  lamp  be 
to  that  of  the  candle  as  2500  is  to  2025,  or  as  1-234  is  to  1. 

This  method  is  founded  upon  the  fact  to  be  illustrated  in  the 
next  paragraph,  that  the  intensity  of  the  light  from  any  luminous 
body,  at  different  distances,  will  be  inversely  as  the  squares  of 
those  distances. 

The  experiment  must,  of  course,  be  conducted  in  a  dark  room. 

QUESTIONS. — Describe  the  method  -of  determining  the  comparative 
intensities  of  two  lights  by  a  comparison  of  the  shadows  they  produce. 


DISTRIBUTION     OF    LIGHT.  65 


DISTRIBUTION    OF    LIGHT. 

68.  Light  is  distributed,  or  diffused  abroad,  by  several  modes ; 
as  by  radiation,  reflection,  refraction,  &c. 

Light  emanates  from  every  point  in  the  surface  of  a  luminous 
body,  and  is  equally  distributed  on  all  sides,  if  not  intercepted, 
diverging  like  radii  drawn  from  the  centre  to  the  surface  of  a 
sphere.  Thus,  if  a  single  luminous  point  were  placed  in  the 
centre  of  a  hollow  sphere,  every  point  of  its  concavity  would  be 
illuminated,,  and  equal  areas  would  receive  equal  quantities  of 
light.  Each  ray,*when  not  interrupted  in  its  course,  and  while 
it  remains  in  the  same  medium,  moves  in  a  straight  line,  as  is 
obvious  by  the  appearance  of  shadows  cast  by  the  side  of  a  house, 
or  of  a  sun-beam  admitted  through  a  small  aperture  into  a  dark 
room.  Owing  to  these  modes  of  distribution,  it  follows  that  the 
quantity  of  light  which  falls  upon  a  given  surface  decreases  as  the 
square  of  its  distance  from  the  luminous  object  increases — the  same 
law  which  regulates  the  heating  power  of  a  hot  body. 

69.  The  passage  of  light  is  progressive,  time  being  required  for 
its  motion  from  one  place  to  another.     It  comes  to  the  earth  from 
the  sun  in  about  8£  minutes, — a  distance  of  95,000,000  miles, — 
which  shows  its  rate  of  progress  to  be  about  195,000   miles  a 
second.     Owing  to  this  prodigious  velocity,  the  light  caused  by 
the  firing  of  a  cannon  or  a  sky-rocket  is  seen  by  different  specta- 
tors at  the  same  instant,  whatever  may  be  their  respective  dis- 
tances from  the  rocket,  the  time  required  for  light  to  travel  100 
or  1000  miles  being  inappreciable  to  our  senses. 

70.  Reflection  of  Light.— Light  is  reflected  in  the  same  man- 
ner as  heat  (31),  obeying  precisely  the  same  laws.     This  always 
takes  place  when  it  passes  from  one  medium  into  another  of  dif- 
ferent nature  or  density,  whether  the  media  be  solid,  liquid,  or 
gaseous.     Different  media,  however,  differ  much  in  their  power 
of  reflection. 

Bright  metallic  surfaces,  as  polished  silver  or  clean  mercury, 

QUESTIONS. — 68.   How  is  light  distributed  ?     Does  light  emanate  from 
every  point  of  an  object?     What  is  said  of  the  course  of  a  ray  when  not 
interrupted  ?     69.   Is  the  passage  of  light  from  point  to  point  instanta- 
neous?    What  is  its  velocity?     70.  When  is  light  said  to  be  reflected? 
G* 


66 


DISTRIBUTION    OF    LIGHT. 


,"' 
'A'.  B 

Iteflection  of  Light. 


reflect  nearly  all  the  rays  which  fall  upon  them  ;  while  those 
which  are  dull  and  rough  reflect  but  a  few.  The  reflection  of 
light,  like  that  of  heat,  takes  place  at  the  surface  of  bodies,  arid 
appears  to  be  influenced  rather  by  the  condition  of  the  surface 
than  by  the  internal  nature  or  structure  of  the  reflecting  body. 

Let  A  15  be  the  reflecting  surface, 
E  C  the  ray  incident  at  C,  and  C  D  the 
reflected  ray,  and  let  P  C  be  perpen 
dicular  to  AB.  ECP  will  then  be 
the  angle  of  incidence,  and  PCD  the 
angle  of  reflection,  both  of  which  will 
be  equal.  It  is  not  necessary  tiiat  the 
reflecting  surface  should  be  a  plane,  as 
might  be  supposed; — it  may  be  either  concave,  as  a  b,  or  convex, 
as  A'  B',  and  the  same  results  would  follow. 

Light  has  precisely  the  same  characters  after  being  reflected  a? 
before,  but  is  less  intense,  because  of  the  absorption  of  a  part  of 
the  rays. 

71.  Refraction  of  Light. — When  a  ray  of  light  passes  through 
the  same  medium,  as  glass  or  water,  or  when  it  passes  perpen- 
dicularly from  one  transparent  medium  to  another,  it  moves  in 
perfectly  straight  lines ;  but  wnen  it  passes  obliquely  from  one 
medium  to  another  of  different  density,  it  is  thrown  more  or  less 
out  of  its  first  direction,  and  is  said  to  be  refracted. 

Thus,  a  ray  of  light,  R,  passing  through 
the  air,  when  ifc  comes  in  contact  with  a 
piece  of  polished  glass  at  A,  does  not  move 
on  in  a  straight  line  to  R',  but  is  bent 
downward  or  refracted,  and  emerges  from 
the  glass  at  B,  where  it  is  again  refracted 
in  the  opposite  direction,  and  takes  the 
same  course,  though  not  precisely  the  same  path,  as  it  had 
at  first. 

Refraction  always  takes  place  when  a  ray  of  light  passes  obliquely 
from  one  medium  to  another  of  different  density,  but  not  always  to 
the  same  amount;  this  will  depend  upon  the  refracting  power  of 


Refraction  of  Light. 


QUESTIONS. — Describe  the  angles  of  incidence  and  reflection.     71.  When 
is  light  said  to  be  refracted? 


DISTRIBUTION    OF    LIGHT.  67 

the  two  media,  and  also  upon  the  obliquity  of  the  ray  to  the  sur- 
faces of  the  media  in  contact. 

When  the  ray  passes  from  a  rare  to  a  dense  medium,  it  is  always 
refracted  or  bent  towards  a  line  perpendicular  to  the  surface  at  the 
point  of  contact,  and  from  this  line  when  it  passes  in  the  opposite 
direction,  from  a  dense  to  a  rare  medium. 

To  understand  the  relative  positions  of  the  incident  and  th 
refracted  ray,  in  the  case  of  any  two  media,  the  following  la^v 
needs  to  be  well  studied.     Let  A  B  in  the  figure  be  the  surface 
of  some  transparent  medium  more 
dense  than  air,  as  water,  and  let 
I  C  be  a  ray  of  light  incident  upon 
it  at  C }  it  will  not  pass  on  in  a 
straight  line,  but  on  entering  the 
water  will  be  bent  downward,  to 
E ;  I  C  is  then  called  the  incident 
ray,   and   C  E   the  refracted   ray. 
Let  P  P'  be  a  line  perpendicular 
to  the  surface   at  C,  then  angle  index  of  Refraction. 

ICP  will  be  the  angle  of  incidence,  and  ECP'  the  angle  of 
refraction. 

If  now  from  C  as  a  centre  we  draw  the  circle  A  P  B  P',  and 
also  the  lines  I  a  and  E  c  both  at  right  angles  to  P  P',  then  will 
I  a  be  the  sine  of  the  angle  of  incidence  and  E  c  the  sine  of  the 
angle  of  refraction.  And  for  the- same  two  media  these  lines  will 
always  have  the  same  ratio  to  each  other,  whatever  may  be  the 
angle  of%  incidence.  Thus,  if  a  second  ray,  i  C  be  incident  at  C, 
it  will  emerge  at  e;  and  the  sines  of  the  angles  of  incidence  and 
refraction,  that  is,  the  lines  i  b  and  e  d  will  have  to  each  other 
the  same  ratio  as  the  lines  I  a  and  EC;  and  the  same  will  be 
true  for  the  same  media,  whatever  may  be  the  angle  of  the  inci- 
dent ray. 

The  quotient  obtained  by  dividing  the  sine  of  the  angle  of  inci- 
dence by  that  of  the  angle  of  refraction  is  called  the  index  of 
refraction  for  the  media  used ;  for  the  same  media  it  is  always 

QUESTIONS. — What  is  the  course  of  the  ray  in  passing  from  a  rare  to  a 
dense  medium  ?  When  from  a  dense  to  a  rare  medium  ?  Describe  the 
angles  of  incidence  and  of  refraction.  Describe  the  index  of  refraction. 


G8 


DECOMPOSITION    OF    LIGHT. 


the  same,  but  varies  with  different  media.  Usually  tho  air  is 
taken  as  one  of  the  media,  so  that  the  index  of  refraction  for  any 
substance  is  the  quotient  thus  obtained  in  tho  case  of  a  ray  of 
light  in  passing  from  air  into  that  substance.  The  index  of 
refraction  for  water  is  thus  found  to  be  133,  for  common  flint 
glass  1-56,  for  oil  of  cassia  1-64,  for  phosphorus  2-22,  and  for  the 
diamond  2 '43. 

(For  the   Polarization  of  Light,  see  the  author's  "Natural 
Philosophy:') 


DECOMPOSITION     OF    LIGHT. 

72.  The  Solar  Spectrum.  —  The  white  light  of  the  sun  is  not  a 
homogeneous  substance,  but  is  capable  of  being  separated  into 
several  rays  of  entirely  different  colors.  This  was  first  effected 
by  Newton,  by  passing  it  through  a  triangular  piece  of  clear,  solid 
glass,  called  a  prism. 

In  the  figure  following,  let  S  be  a  ray  of  light  from  the  sun, 

admitted  into  a  darkened 
room  through  the  window- 
shutter,  D  E  ;  it  will  pass 
downward  to  the  floor,  at  a 
little  distance  from  the  wall, 
producing  a  circular  spot  of 
clear  white  light,  W.  Then 
let  the  prism  A  B  C.  be  held 
in  the  ray,  and  at  once  the 

fP0*  at  W  wil1  disaPPear>  and, 

in  its  stead,  an  elongated  and 
beautifully  colored  image  of  the  sun  will  be  seen  upon  a  screen 
hung  up  in  front  of  the  window,  or  on  the  wall  at  the  opposite 
side  of  the  room,  if  no  screen  be  used.  The  several  colors  will 
appear  in  the  order  indicated,  the  violet  being  uppermost  and  the 
red  lowest. 

QUESTIONS.  —  What  is  the  index  of  refraction  for  water?  Flint-glass? 
Diamond  ?  72.  How  may  light  be  decomposed  ?  Describe  the  exDeri- 
•ncnt  .with  the  prism. 


Decomposition  of  Light. 


DECOMPOSITION     OF    LIGHT.  69 

It  will  be  seen  that  the  light,  in  passing  the  prism,  lias  been 
twice  refracted,  or  bent  upward,  first  as  it  entered  the  glass,  and 
a<r,iin  as  it  issued  from  it ;  and  that  the  separation  of  the  several 
colors  has  been  in  consequence  of  their  different  refrangibilities. 
The"  violet  being  most  refrangible,  is  found  uppermost  in  the 
picture,  and  the  red  is  lowest,  because  least  refrangible.  The 
other  colors  occupy  intermediate  positions,  depending  upon  their 
respective  refrangibilities. 

The  colored  image  thus  produced  is  called  the  solar  spectrum  / 
and,  according  to  Newton,  it  is  composed  of  the  seven  colors 
named  in  the  figure,  which  are  therefore  called  primary  colors. 

73.  More  recent  investigations  by  Brewster  render  it  probable 
that  there  are  in  the  spectrum  really  only  three  colors,  red,  yellow, 
and  blue,  and  that  the  other  shades  are  produced  by  mixtures  of 
these  in  different  proportions;  a  mixture  of  the  blue  and  the  yel- 
low, for  instance,  producing  the  green,  and  a  like  mixture  of  the 
red  and  yellow  producing  the  orange.     Indeed,  it  is  believed  that 
each  of  these  three  colors  extends  over  the  whole  spectrum,  but 
each  is  much  more  intense  at  one  part  of  the  spectrum  than  else- 
where, the  blue  being  most  intense  near  the  top,  and  the  red  near 
the  bottom,  with  the  most  intense  portion  of  the  yellow  between 
them.     The  solar  spectrum,  therefore,  as  produced  by  the  prism, 
may  be  considered  as  composed  of  three  simple  spectra  super- 
imposed upon  each  other. 

The  distribution  of  the  rays  in  each  of      B  TT  at. 

these  simple  spectra  is  represented  by  the 
shading  of  the  annexed  figures,  in  which  B 
represents  the  blue,  Y  the  yellow,  and  K, 
the  red,  each  color  being  supposed  to  be 
separated  from  the  others.  If  the  three 
spectra  be  thrown  one  upon  another  on  the 
same  screen,  the  ordinary  solar  spectrum 

will  be  produced.  Colors  of  Spectrum. 

74.  Heating  and  Chemical  Rays. — It  has  been  stated  above 
that  light   is   capable  of  producing   several  distinct   classes  of  ' 

QUESTIONS. — What  are  Newton's  primary  colors?  Why  are  these  sepa- 
rated by  the  prism  ?  73.  What  colors  only  are  contained  in  the  spectrum, 
according  to  Brewster  ?  How  are  the  other  colors  produced  ?  74.  In  what 
part  of  the  spectrum  are  the  greatest  heating  effects  produced  ? 


70  DECOMPOSITION    OF    LIGHT. 

effects,  as  those  of  color,  those  of  heat,  and  besides  these,  others 
•which  may  strictly  be  called  chemical  effects.  Now,  these  several 
effects  are  not  produced  in  every  part  of  the  spectrum  with  equal 
facility;  the  greatest  illuminating  power  is  found  to  be  in  the  yel« 
low,  while  the  greatest  heat  is  in  the-red,  or  a  little  below  it,  and 
the  greatest  chemical  effects  are  produced  in  the  extreme  violet. 

The  chemical  effects  of  light  are  various  and  important ;  a  mix- 
ture of  chlorine  and  hydrogen  gases  may  be  kept  together  in  the 
dark  for  any  length  of  time,  without  combining,  but  unite  with 
an  explosion  when  placed  in  the  direct  sunlight.  On  the  other 
hand,  many  compound  substances  are  decomposed  by  light,  as 
certain  preparations  of  gold  and  silver.  If  a  piece  of  white  paper 
be  coated  over  with  a  thin  film  of  white  chloride  of  silver,  care- 
fully prepared  in  the  dark,  and  then  placed  in  the  solar  spectrum, 
the  part  in  the  violet  ray  will  soon  become  black,  while  that  in  the 
red  will  scarcely  be  affected.  Between  these  extremes  there  will 
be  produced  various  shades  of  gray  and  purple. 

It  appears,  therefore,  that  the  sun's  light  is  made  up  of  three 
kinds  of  rays,  viz.,  the  colorific  rays,  or  rays  of  light  proper,  the 
heating  rays,  and  the  chemical  rays,  the  last  of  which  are  most, 
and  the  heating  rays  least,  refrangible. 

The  light  of  the  sun  produces  most  important  effects  in  the  vegetable 
world ;  many  plants  will  not  grow  in  the  dark,  and  others  growing  in  the 
shade  have  their  nature  entirely  changed.  But  a  discussion  of  these 
topics  does  not  belong  to  our  present  subject. 

75.  Photography. — By  this  name  we  designate  the  various 
modes  of  producing  pictures  by  the  action  of  light.  If  a  piece 
of  white  paper  is  moistened  with  a  dilute  solution  of  common  salt, 
and  then  one  side  of  it  washed  with  a  solution  of  nitrate  of  silver, 
the  surface  becomes  coated  with  chloride  of  silver,  which  readily 
turns  black  or  dark  chestnut  by  exposure  to  the  direct  rays  of  tho 
sun.  If,  now,  before  exposing  paper  thus  prepared  to  the  light, 
any  small  flat  object,  as  a  flower,  or  piece  of  lace,  be  placed  upon  it, 
an  image  of  the  object  will  remain  upon  the  paper,  and  may  bo 

QUESTIONS. — In  what  part  of  the  spectrum  are  the  greatest  chemical 
effects  produced  ?  Does  the  light  of  the  sun  produce!  any  important 
effects  upon  vegetable  bodies  ?  75.  What  is  photography  ?  What  method 
is  mentioned  for  preparing  a  photographic  paper  ? 


DECOMPOSITION    OF    LIGHT.  71 

rendered   permanent  by  soaking  it  immediately  in  a  saturated 
solution  of  common  salt,  or  of  iodide  of  potassium. 

The  unaltered  e"hloride  of  silver  in  the  paper  is  by  this  soaking 
dissolved  out,  while  the  part  that  has  become  colored  resists  the 
action  of  the  solvent  and  therefore  remains  in  the  paper. 

Talbot's  Calotype  Process,  invented  by  a  gentleman  of  this 
name,  is  conducted  as  follows :  A  sheet  of  writing  paper  of  a 
firm  texture  is  brushed  over  on  one  side  with  a  solution  of  50 
grains  of  nitrate  of  silver  in  an  ounce  of  water,  and  then  dried 
in  a  dark  room,  and  subsequently  soaked  two  or  three  minutes 
in  a  solution  of  iodide  of  potassium,  containing  about  an  ounce 
of  the  iodide  to  a  pint  of  distilled  water.  It  is  then  to  be  again 
soaked  for  some  minutes  in  water,  and  thoroughly  dried,  and 
preserved  for  use. 

When  required  for  use,  the  paper  is  to  be  washed  on  the  side 
previously  iodized  by  gallo-nitrate  of  silvery  prepared  for  the 
occasion  in  the  following  manner :  Dissolve  100  grains  of  nitrate 
of  silver  in  2  ounces  of.  distilled  water,  and  add  to  it  an  equal 
volume  of  strong  acetic  acid,  and  then  mix  with  it  several  volumes 
of  saturated  solution  of  gallic  acid  in  cold  distilled  water.  This 
last  preparation  should  be  made  only  in  small  quantity  for  the 
particular  occasion,  as  it  spoils  by  keeping.  The  last  washing 
should  be  made  in  the  dark,  or  with  only  a  feeble  candle  light; 
and  the  paper  dried  carefully,  excluding  the  light  of  day,  to  the 
action  of  which  it  is  exceedingly  sensitive. 

Paper  prepared  in  this  way  may  be  used  in  the  manner  first 
described,  or  in  the  camera  obscura,  for  the  taking  of  portraits. 
If  the  picture  at  first  is  not  sufficiently  distinct,  it  may  b^  improved 
by  washing  it  again  in  the  gallo-nitrate  of  silver.  Finally,  it  is 
to  be  rendered  permanent  by  washing  it  with  solution  of  bromide 
of  potassium,  or  of  common  salt. 

The  picture  thus  formed  is  what  is  called  a  negative  picture— 
that  is,  the  light  and  shade  are  reversed,  as  compared  with  an 
ordinary  engraving;  but  a  positive  one. may  be  formed  from  the 
first  by  using  it  as  an  object  for  forming  a  second  picture  upon 
another  sheet  of  the  same  prepared  paper.  For  this  purpose  it  is 

QUESTIONS. — Describe  Talbot's  Calotype  process.  What  are  negation 
and  what  positive  pictures? 


72  DECOMPOSITION     OF    LIGHT. 

placed  with  its  face  downward  upon  the  prepared  paper,  and  then 
exposed  to  the  direct  rays  of  the  sun,  as  directed  above  (75).  The 
new  picture  is  to  be  rendered  permanent  in  tEe  same  manner  as. 
before. 

Numerous  other  preparations  are  in  use  for  producing  pictures  upon 
paper,  but  none  of  them  equal  in  sensitiveness  the  one  just  described. 
Though  the  materials  to  be  used  are  different,  as  well  as  the  processes, 
yet  the  essential  principles  are  the  same  in  all.  The  light  produces  a 
chemical  change  in  the  parts  of  the  picture  exposed  to  its  influence,  and 
the  picture  is  fixed  by  soaking  the  paper  in  a  solution  capable  of  dis- 
solving out  the  sensitive  substance  contained  in  the  parts  which  have  not 
undergone  this  change,  in  consequence  of  being  in  the  shade. 

Paper  prepared  for  the  taking  of  pictures  is  called  photogenic  paper, 
and  generally  cannot  be  long  kept,  even  in  the  dark. 

76,  The  Daguerreotype  process,  so  called  from  the  name  of  the 
inventor,  is  applied  only  to  plates  of  silver,  which  are  usually 
spread  upon  plates  of  copper.  The  silver  surface  is  first  very 
thoroughly  cleaned  by  washing  with  dilute  nitric  acid,*  and  rub- 
bing with  leather  or  cotton  and  some  polishing  substance,  as  very 
fine  colcothar.  It  is  then  to  be  subjected  for  a  few  minutes  to  the 
action  of  vapor  of  iodine,  by  placing  it  in  a  box  which  has  some 
crystals  of  iodine  spread  upon  the  bottom;  by  this  means,  an 
exceedingly  thin  coating  of  iodide  of  silver  is  .formed  upon  the 
surface  of  a  straw-yellow  color,  which  is  very  sensitive  to  the 
action  of  light.  It  is  then  placed  in  a  camera  obscura,  and  the 
image  of  any  object  in  front  is  made  to  fall  upon  it  for  a  few 
moments,  by  which  such  a  chemical  change  is  produced  in  the 
thin  coating  of  iodide  of  silver,  that  subsequent  exposure  to  the 
vapor  of  mercury,  at  about  165°  F.,  brings  out  a  beautiful  picture 
of  the  object.  By  close  inspection,  it  will  be  found  that  in  the 
parts  of  the  picture  where  the  most  light  has  fallen  such  a  change 
has  been  produced  that  the  mercury  is  capable  of  acting  upon  it, 
but  in  other  parts  the  bright  surface  of  the  silver  remains  un- 
affected; and  further,  the  action  of  the  mercury  upon  the  silver 
plate  will  be  in  proportion  to  the  intensity  of  the  light  upon  the 
different  parts. 

*-  Instead  of  pure  iodine,  the  bromide  or  chloride  of  iodine  may 
be  used  for  preparing  the  plates  j  but  the  last  compound  is  said  to 
be,  on  the  whole,  much  the  best. 

QUESTIONS. — How  are  pictures  prepared  in  this  way  fixed  or  rendered 
permanent  ?  76.  Describe  the  Daguerreotype  process. 


DECOMPOSITION    OF    LIGHT.  73 

The  picture,  when  taken  from  the  mercurial  process,  is  rendered 
permanent  by  removing  the  coating  of  iodide  of  silver,  which  is 
readily  done  by  merely  pouring  over  it  a  warm  solution  of  hypo- 
sulphite of  soda  or  of  common  salt. 

It  is  further  improved,  and  the  shades  rendered  deeper,  by 
heating  upon  it  a  solution  of  chloride  of 'gold  and  hyposulphite 
of  soda. 

The  Daguerreotype  process  is  very  simple,  but  to  insure  sue 
cess,  close  attention  must  be  paid  to  various  minute  particulars, 
which  cannot  here  be  discussed. 

77.  Thermograpliy  is  a  name  which  has  been  given  to  certain  modes, 
dependent,  it  is  believed,  upon  heat,  by  which  one  body  is  made  to  depict 
itself  more  or  less  minutely  upon  another,  either  in  contact  with  it  or  in 
its  vicinity.     Thus,  if  we  write  with  some  soft  substance  upon  glass,  and 
then  breathe  upon  it,  the  writing  becomes  visible.     So  if.we  allow  a  piece 
of  coin  to  lie  for  a  time  on  a  plate  of  metal  or  glass,  and  then  breathe 
upon  it,  an  image  of  the  coin  will  be  produced.     If  while  the  piece  of  coin 
lies  upon  the  metallic  plate  it  is  gently  heated  by  a  spirit-lamp,  and  when 
cold  exposed  to  the  vapor  of  mercury,  a  very  distinct  image  of  the  coin 
will  be  formed.     In  some  cases,  we  are  told,  this  effect  will  be  produced 
when  the  coin  has  not  touched  the  plate,  but  only  remained  for  a  time 
near  it. 

78.  Double  Refraction  of  light  takes  place  when  a  ray  is  passed 
through  certain  transparent  crystals,  and  some  organized   sub- 
stances, so  that  objects  seen  through  them  in  particular  directions 
appear  double ;  and  the  rays  emerging  from  them  are  found  to 
have  undergone  a  further  change,  by  which  they  have  acquired 
peculiar  properties  on  different  sides,  and  are  said  to  be  polarized. 
Light  is  also  polarized  by  other  means,  as  by  reflection  at  particular 
angles  from  most  non-metallic  substances,  and  by  refraction.    For 
a  very  full  discussion  of  the  subject,  see  Natural  Philosophy, 
page  259. 

Rays  of  heat  may  be  polarized  in  the  same  manner  and  by  the 
same  means  as  those  of  light. 

QUESTIONS.— 77.  What  is  thermography?  78.  When  is  light  said  to  be 
doubly  refracted  f 


74  NATURE    OP    ELECTRICITY. 


III.   ELECTRICITY. 

NATURE     OP     ELECTRICITY.  —  ELECTRICAL 
THEORIES. 

-,  79.  Nature  of  Electricity.  —  As  in  the  "cases  of  heat  and  light, 
we  know  nothing  of  the  real  nature  of  electricity,  all  our  know- 
ledge on  the  subject  being  limited  to  its  effects. 

Like  heat  and  light,  it  is  imponderable  ;  no  accumulation  of  it 
in  any  substance  adds  to  the  weight  of  that  substance,  even  when 
tried  by  the  most  delicate  balances;  but  many  of  its  effects  are  so 
like  those  of  a  mechanical  agent,  that  it  is  usually  considered  a 
separate  material  substance. 

When  certain  substances,  such  as  amber,  glass,  sealing-wax, 
and  sulphur,  are  rubbed  with  dry  silk  or  cloth,  they  are  found  to 
have  acquired  a  property,  not  observable  in  their  ordinary  state, 
of  causing  contiguous  light  bodies  to  move  towards  them  ;  or,  if 
the  substances  so  rubbed  be  light  and  freely  suspended,  they  will 
move  towards  contiguous  bodies.  After  a  while  this  curious  phe- 
nomenon ceases  ;  but  it  may  be  renewed  an  indefinite  number  of 
tintes  by  friction.  This  property  was  first  noticed  in  amber;  and 
therefore  the  principle  thus  developed  was  called  electricity  (from 
the  Greek,  electron,  amber). 

When  a  substance,  by  friction  or  other  means,  has  acquired  the 
property  just  stated,  it  is  said  to  be  electrified,  or  to  be  electrically 
excited  ;  and  its  motion  towards^other  bodies,  or  of  other  bodies 
towards  it,  is  ascribed  to  a  force  called  electric  attraction.  But  its 
influence,  on  examination,  will  be  found  to  be  not  merely  attractive; 
on  the  contrary,  light  substances,  after  touching  the  electrified  body, 
will  be  disposed  to  recede  from  it  just  as  actively  as  they  approached 
it  before  contact.  This  is  termed  electric  repulsion. 

80.  Theories  of  Electricity.  —  In  the  absence  of  positive  know- 
Jodge  in  regard  to  the  nature  of  this  agent,  two  theories  have  been 
,..  ,  ^osed,  to  account  for  and  connect  together  the  established  facts. 


.  —  79.  Do  we  understand  the  real  nature  of  electricity?  Is 
it  Imponderable  ?  What  is  the  derivation  of  the  term  electricity  ?  "When 
is  a  substance  said  to  be  excited  or  electrified  ? 


ELECTRICAL    THEORIES. 


75 


Dnfagfs  theory  (from  the  name  of  its  proposer)  supposes  that 
every  substance,  in  its  natural  state,  contains  in  itself  two  highly 
subtile  and  elastic  fluids,  in  such  a  state  of  combination  that  their 
presence  is  entirely  disguised;  but  that  the  various  phenomena 
of  electrical  excitement  are  produced  by  one  or  the  other  of  them, 
accumulated  in  a  body  in  excess.  The  particles  of  each  fluid  are 
supposed  to  have  a  strong  attraction  for  those  of  the  opposite  kind, 
and  for  other  matter,  but  are  highly  repulsive  of  each  other. 

These  fluids  are  supposed  to  be  separated  by  the  various  modes 
of  producing  electrical  excitement,  to  be  hereafter  described ;  and 
one  of  them  being  collected  in  excess  in  a  body,  as  just  stated, 
produces  the  phenomena  witnessed. 

In  most  cases,  when  glass  or  any  other  vitreous  substance  13 
rubbed,  the  electricity  which  is  collected  is  the  reverse  of  that 
obtained  when  sealing-wax  is  subjected  to  friction ;  and  hence  the 
former  is  called  vitreous,  and  the  latter  resinous  electricity. 

Franklin's  tlieory  of  electricity  supposes  that  all  bodies,  in  their 
natural  state,  contain  in  their  substance  a  certain  quantity,  called 
their  natural  share,  of  a  single,  subtile,  elastic  fluid,  which  pro- 
duces no  sensible  effects;  but  that  the  phenomena  of  electrical 
excitement  are  produced  when  the  body  is  made  to  contain  either 
less  or  more  than  its  natural  share.  It  supposes  that  the  particles 
of  this  fluid  repel  each  other  strongly,  but  are  attracted  by  all 
other  matter.  When  a  body  contains  more  than  its  natural  share, 
it  is  said  to  be  positively  electrified ;  and  negatively  electrified, 
when  it  contains  less. 

Glass  and  other  vitreous  substances,  when  rubbed,  are  supposed 
to'  take  more  than  their  natural  share  of  the  fluid,  or  become 
positive;  while  resinous  substances,  in  the  same  circumstances, 
lose  a  portion  of  their  natural  electricity,  or  become  negative. 
These  states  are  often  indicated  by  the  algebraic  signs  -f-  and  — . 

The  terms  vitreous  and  positive,  of  the  two  theories,  are  there- 
synonymous,  as  are  also  the  terms  resinous  and  negative. 

Either  of  these  theories  is  found  to  answer  well  in  explaining 
most  of  the  phenomena  of  electricity,  but  that  of  Dufay  is  gene- 

QUESTIONS.  —  80.  Describe  Dufay's  theory  of  electricity.  Describe 
F'  -.nldin's  theory.  What  terms  were  proposed  by  him?  What  terms  of 
tJ  two  theories  are  synonymous  ' 


76  DISTRIBUTION    OF    ELECTRICITY. 

rally  preferred ;  though  the  terms  positive  and  negative,  of  Frank- 
lin's theory,  are  almost  universally  used. 

From  the  above  it  will  readily  be  seen,  that  when  two  bodies 
are  either  positively  or  negatively  electrified,  they  repel  each 
other,  bat  attract  each  other  when  one  is  positive  and  the  other 
negative. 

81.  Electrometers, — Electrometers  are  instruments  for  indi- 
cating the  presence  of  electricity,  or  its  intensity.  A  pith-ball,  sus- 
pended by  a  dry  silk  thread  from  any  convenient  support,  answers 
the  purpose  quite  well ;  but  the  following,  called  the 
gold-leaf  electrometer,  is  a  -more  sensitive  instrument. 
It  consists  of  two  slips  of  gold-leaf,  suspended  in  a 
cylindrical  glass  vessel,  from  a  metallic  plate  at  the 
top.  If  the  bottom  is  also  made  of  metal,  its  sensi- 
tiveness will  be  increased.  When  an  excited  body  is 
brought  near  the  metallic  plate,  the  leaves  at  once 
diverge,  in  consequence  of  their  being  brought  Into 
the  same  state,  whether  positive  or  negative,  by  the 

Electrometer.  6  >    .J 

•   inductive  influence  of  the  excited  body,  in  a  manner 
to  be  hereafter  explained. 


DISTRIBUTION    OP    ELECTRICITY. 

82.  Conduction  of  Electricity. —  Some  substances  allow  the 
electric  fluids  to  pass  over  them  freely,  and  are  therefore  called 
conductors;  while  others,  that  do  not  possess  this  property,  or 
only  imperfectly,  are  called  non-conductors.  If  electricity  be  im- 
parted to  one  end  of  a  conductor,  such  as  a  copper  wire,  the  other 
extremity  of  which  touches  the  ground,  or  is  held  by  a  person 
standing  on  the  ground,  the  electricity  will  pass  along  its  whole 
length  and  escape  in  an  instant,  though  the  wilfe  were  several 
miles  long;  whereas  excited  glass  and  resin,  which  are  non-con- 
luctors,  may  be  freely  handled  without  losing  any  electricity 
except  at  the  parts  actually  touched. 

QUESTIONS.  —  "Which  of  these  theories  is  now  generally  preferred? 
When  do  bodies  attract  and  when  repel  each  other?  81.  What  are 
electrometers  ?  Describe  the  gold-leaf  electrometer.  82.  What  is  said  of 
the  conduction  of  electricity  ?  What  are  conductors  and  non-conductors  ? 


DISTRIBUTION    OF    ELECTRICITY.  77 

% 

To  the  class  of  conductors  belong  the  metals,  charcoal,  plum- 
bago, water,  and  aqueous  solutions,  and  substances  generally 
which  are  moist,  or  contain  water  in  its  liquid  state,  such  as 
animals  and  plants,  and  the  surface  of  the  earth.  These,  how- 
ever, differ  in  their  conducting  power.  Of  the  metals,  silver  and 
copper  are  found  to  be  the  best  conductors ;  and  after  these  follow 
gold,  zinc,  platinum,  iron,  tin,  lead,  antimony,  and  bismuth 
Aqueous  solutions  of  acids  and  salts  conduct  much  better  than 
pure  water. 

To  the  list  of  non-conductors  belong  glass,  resins,  sulphur, 
diamond,  dried  wood,  precious  stones,  earth,  and  most  rocks  when 
quite  dry,  silk,  hair,  and  wool.  Air  and  gases  in  general  are 
non-conductors  if  dry,  but  act  as  conductors  when  saturated  with 
moisture. 

It  is  not,  however,  to  be  understood  that  any  very  definite  line  can  be 
drawn  between  the  two  classes  of  conductors  and  non-conductors ;  but 
there  seems  to  be  a  very  regular  gradation  from  the  most  perfect  con- 
ductor to  the  most  imperfect,  or  most  perfect  non-conductor.  This 
division  of  substances  is,  however,  found  very  convenient,  though  in  some 
instances  individuals  might  differ  with  regard  to  the  class  to  which  a 
particular  substance  should  be  assigned. 

83.  Insulation, — When  a  conductor  is  supported  upon  a  non- 
conducting substance,  it  is  said  to  be  insulated,  and  electricity 
may  be  retained  upon  it  for  a  time;  but  even  then  it  will  be 
gradually  diffused  and  disappear.  This  is  occasioned  in  part  by 
the  conducting  power  of  the  air,  which  is  considerable,  except 
when  it  is  very  dry.  In  damp  weather,  many  electrical  experi- 
ments cannot  well  be  performed,  because  of  the  rapid  diffusion  of 
the  fluid  through  the  air,  and  the  deposition  of  moisture  upon  the 
surfaces  of  insulators. 

When  two  substances  are  rubbed  together,  both  electricities  are 
always  developed,  one  of  them  going  to  one  of  the  substances,  and 
the  other  "to  the  other  substance ;  and  both  electricities  maybe 
retained,  if  the"  two  substances  rubbed  together  are  insulated. 

QUESTIONS. — What  substances  are  classed  with  conductors,  and  what 
with  non-conductors  ?  Can  any  definite  line  be  drawn  between  the  con- 
ductors and  non-conductors  ?  83.  When  is  a  body  said  to  be  insulated  ? 
Why  do  electrical  experiments  often  fail  in  damp  weather  ?  Are  both 
electricities  always  developed  by  friction? 

7* 


78 


DISTRIBUTION    OF    ELECTRICITY. 


-f 


Induction  of  Electricity. 


84.  Induction  of  Electricity,  —  An  electrified  body  always 
exerts  a  peculiar  influence  on  the  natural  electricity  of  other 
bodies  in  its  vicinity,  called  induction,  the  nature  of  which  will 
be  seen  from  the  following  explanation :  Let  A  be  a  positively 
excited  glass  tube,  held  near  one  end 
of  an  insulated  conductor,  B,  supposed 
to  be  in  its  natural  state;  the  natural 
electricity  in  B  will  instantly  be  dis 
turbed,  and,  on  examination,  it  will  be 
found  ^that  the  end  next  the  excited 
glass  is  negatively  electrified,  and  the 
other  end  positively,  as  shown  by  the 
algebraic  signs.  If,  instead  of  the  glass 
tube,  some  other  substance,  negatively 
electrified,  had  been  used,  the  elec- 
tricities of  the  two  ends  of  the  conductor  B  would  have  been 
reversed.  In  every  case,  the  part  of  the  conductor' next  to  the 
excited  body  will  be  in  the  opposite  state  of  excitement,  while  the 
other  end  will  be  in  the  same  state  as  the  excited  body. 

In  the  experiment  nothing  but  air  is  supposed  to  be  between  the 
excited  body  A,  and  the  conductor  B,  but  the  inductive  influence 
is  exerted  through  all  non-conductors.  Thus,  if  a  clean  and  dry 
pane  of  glass  be  held  between  A  and  B,  the  result  will  be  the  same. 

Let  A  and  B,  in  the  next  figure,  be  two 
metallic  discs,  supported  upon  pillars  of 
glass,  their  edges  being  towards  the  eye, 
and  let  a  spark  of  positive  electricity  be 
communicated  to  one  of  them,  as  A; — it 
will  immediately  act  by  induction  upon 
the  natural  electricity  of  B,  causing  the 
side  next  to  A  to  be  negative  and  the 
other  to  be  positive.  The  effect  is  pre- 
cisely the  same  as  in  the  preceding 
experiment,  but  the  form  of  the  con- 
ductors different.  If  now  we  touch  the 


irailffilB  •••••I 

Induction  of  Electricity. 


QUESTIONS. — 84.  What  is  meant  by  induction?  Explain  the  experi- 
ment described  in  this  paragraph.  Explain  the  experiment  described  in 
connection  with  the  next  figure. 


DISTRIBUTION    OP    ELECTRICITY.  79 

back  of  B  with  the  finger,  the  positive  fluid  escapes,  and  the  whole 
disc  becomes  negative.  The  action  of  the  positive  body,  A,  has 
taken  place  through  the  stratum  of  intervening  air;  and  any  other 
non-conductor  may  be  substituted  for  it.  If,  for  instance,  a  plate 
of  glass  be  interposed,  the  two  plates  may  then  be  brought  much 
nearer  together,  and  the  same  results  will  follow.  Instead  of 
the  metallic  discs,  we  may  simply  apply  a  metallic  coating  to 
the  two  sides  of  a  pane  of  glass ;  which,  if  the  coating  do  not 
reach  within  one  or  two  inches  of  the  edge,  serves  as  a  sufficient 
insulator. 

85.  The  Leyden  Jar. — The  Leyden  jar  receives  its  name  from 
the  city  of  Leyden,  in  Holland,  where  it  was  invented.  It  is 
essentially  the  same  thing  as  just  described,  except  that  a  glass 
jar  is  substituted  in  the  place  of  the  pane.  It  consists  of  a  glass 
jar,  coated  both  inside  and  outside  with  tin-foil, 
except  a  part  around  the  top,  as  shown  in  the 
figure.  Through  a  varnished  wooden  cover,  A, 
a  wire,  having  a  knob  at  top,  is  passed,  and  a 
chain, 'B,  extends  to  the  inside  coating.  Now, 
when  either  positive  or  negative  electricity  is 
communicated  to  the  knob  at  the  top,  it  is  im- 
mediately diffused  over  the  whole  inside  coating; 
and  by  its  inductive  influence,  the  outside  coat- 
ing takes  on  the  opposite  kind.  When  in  this 

.  Leyden  Jar. 

state, — the  two  coatings  being  oppositely  elec- 
trified,—the  jar  is  said  to  be  charged;  and  a  discharge  takes 
place  when  a  communication  is  established  between  the  knob  and 
the  outside  coating,  the  equilibrium  being  restored  with  a  bright 
flash  of  light  and  a  sharp  report.  As  the  human  system  is  a  good 
conductor,  this  discharge  may  take  place  through  it,  by  grasping 
the  outside  coating  with  one  hand,  and  touching  the  knob  at  the 
top  with  the  other ;  or  several  persons  may  form  a  line  by  grasp- 
ing hands,  the  one  at  one  extreme  touching  the  outside  coating, 
while  the  one  at  the  other  extreme  touches  the  knob.  All  will  feel 
the  shock,  as  it  is  called,  at  the  same  instant. 

While  the  jar  is  receiving  the  charge,  it  must  not  be  insulated, 
that  is,  the  outside  must  communicate  with  the  earth.     As  the 

QUESTIONS. — 85.  Why  is  the  Leyden  jar  so  called  ?     Describe  its  con- 
struction  and  use.     How  is  the  shock  produced  in  the  system  i* 


80 


DISTRIBUTION     OF    ELECTRICITY. 


positive  fluid  collects  on  the  inside,  the  outside  becomes  negative 
by  the  expulsion  of  the  positive  fluid  naturally  in  it,  and  the 
accumulation  of  the  negative  fluid  in  its  stead,  drawn  from  the 
earth.  But  if  the  outside  is  insulated  these  transfers  to  and  from 
it  cannot  take  place,  and  therefore  the  jar  cannot  become  charged. 
86,  Free  Electricity  resides  in  the  Surface  of  Bodies.— It  has 
been  demonstrated  that  the  electricity  of  an  excited  body  resides 
entirely  upon  its  surface.  Let  A  be  a  sphere  of  metal,  suspended 
by  a  silk  thread,  and  excited  by  receiving  a  spark  of  electricity  • 
and  let  BB  be  two  covers  of  paper,  gilt  outside  and  inside,  and 
held  by  glass  handles.  Let  them  now  be  applied  to  the  excited 
globe,  and  then  instantly  removed;  it  will  be  found  that  the 
electricity  has  been  entirely  removed  from  the  ball  to  the  covers. 


Resides  upon  the  Surface. 

The  free  electricity  therefore  was  entirely  accumulated  upon  the 

surface  of  the  ball. 

87.  Distribution  over  Surface. — The  fluid  will  be  distributed 
over  the  surface  of  an  excited  conductor,  in 
a  mode  dependent  upon  its  form;  —  if  it 
be  a  perfect  sphere,  the  fluid  will  be  dis- 
tributed equally  over  every  part,  but  if  it 
be  more  or  less  elongated,  as  in  the  prolate 
spheroid,  the  fluid  accumulates  in  the  ends, 
where  the  intensity  is  greatly  increased  if  the 
spheroid  happens  to  be  very  considerably 

Distribution  on  Ellipsoid,    elongated. 

QUESTIONS. — While  receiving  the  charge  must  the  jar  be  insulated? 
Why  ?  86.  In  -what  part  of  an  excited  conductor  does  the  electricity 
reside?  87.  In  what  manner  is  electricity  diffused  over  the  surface  of  a 
sphere?  *How  is  it  diffused  over  the  prolate  spheroid? 


SOURCES     OF     ELECTRICITY.  81 

If  the  extremity  of  the  conductor  is  carried  out  to  a  point,  the 
fluid  at  once  escapes  from  it,  and  all  excitement  disappears,  even 
though  it  remains  insulated.  In  the  same  manner,  a  sharp  point 
projecting  from  a  conductor  receives  the  fluid  silently  upon  it,  and 
the  body  becomes  excited.  The  effect  of  points  in  discharging  or 
receiving  either  of  the  fluids  is  therefore  apparent ;  and  the  circum- 
stance must  always  be  particularly  regarded  in  the  construction  of 
electrical  apparatus. 

The  escape  of  positive  electricity  from  a  point  in  a  \\\  //, 
dark  room  is  always  attended  by  the  appearance  of  a 
faint  blue  light  in  the  form  of  a  brush,  as  represented 
in  A,  but  the  escape  of  the  negative  fluid,  in  the  same 
circumstances,  presents  the  appearance  of  a  star,  as 
shown  in  B. 

It  is  to  be  noticed,  that  in  such  experiments  the 
escape  of.  either  fluid  is  to  be  considered  as  precisely      Electricity 

r  J         on  Points. 

equivalent  to  the  entrance  of  the  other. 


SOURCES     OP     ELECTRICITY. 

88.  As  we  have  seen  above,  electricity  is  believed  to  be  con- 
tained in  all  bodies,  which  are  therefore  properly  its  sources;  but 
the  earth,  as  being  by  far  the  largest  mass  to  which  we  have 
access,   is  its  chief  source.      We   propose,   however,  under  this 
head,  to  speak  of  the  different  modes  of  exciting  or  collecting  it, 
which  are  friction,  change  of  temperature,  and  chemical  action. 

89.  Friction. — It  is  believed  that  electricity  is  always  developed 
when  one  substance  is  rubbed  against  another,  oue  of  the  fluids 
passing  to  one  of  the  substances,  and  the  other  to  the  other  sub- 
stance, as"  before  stated;  but,  in  most  cases,  neither  of  the  fluids 
is  retained,  because  the  rubbing  substances  are  not  insulated.     If 

QUESTIONS. — What  is  the  effect  if  one  part  of  an  insulated  conductor 
is  extended  out  to  a  point  ?  What  is  said  of  the  influence  of  points  in 
receiving  the  fluid  ?  88.  What  is  the  great  source  of  electricity  ?  What 
are  the  different  modes  of  exciting  electricity  ?  89.  Is  electricity  always 
developed  when  one  substance  is  rubbed  against  another?  How  may 
both  be  collected  and  retained  ? 


82 


SOURCES    OP    ELECTRICITY. 


Electrical  Machine. 


both  be  insulated,  both  the  positive  and  negative  fluids  may  be 
retained  (83). 

90.  The  electrical  machine  is  an  instrument  for  developing 
electricity  by  friction  more  abundantly  than  it  can  be  done  by 
the  simple  means  heretofore  pointed  out, 
though  most  of  the  great  principles  of  the 
science,  as  we  have  seen,  may  be  demon- 
strated without  it.  The  figure  in  the  margin 
represents  the  cylinder  machine  in  its  usual 
form.  A  is  a  cylinder  of  glass,  firmly  sup- 
ported, and  capable  of  being  turned  on  its 
axis  by  a  handle;  and  R  is  a  conductor, 
supported  on  a  pillar,  having  the  rubber 
attached  to  it,  with  a  flap  of  silk,  S,  extend- 
ing nearly  over  the  cylinder.  C  is  made 
of  sheet-brass,  and  is  called  the  p*rime  con- 
ductor, because  it  receives  the  electricity 
from  the  cylinder  as  it  is  turned,  by  means 
of  several  pointed  wires  (87),  extending  inwards  towards  the 
cylinder.  It  is  supported  upon  a  pillar  of  glass. 

Now,  when  the  cylinder  is  turned,  electricity  is  abundantly 
developed  by  the  friction  of  the  rubber  against  its  surface,  and  is 
received  by  the  prime  conductor,  in  which  it  accumulates.  The- 
use  of  the  flap  of  silk,  S,  is  to  prevent  the  fluid  from  escaping  in 
the  air,  as  the  cylinder  is  turned. 

From  the  principles  heretofore  discussed,  the  learner  will  readily 
perceive  that  it  is  the  positive  electricity  that  will  be  accumulated 
in  the  prime  conductor;  but  the  negative  (83)  will  also  at  the 
same  time  accumulate  in  the  rubber,  if  it  be  insulated.  But  no 
considerable  quantity  of  electricity  can  usually  be  collected,  unless 
the  rubber  communicates  with  the  earth,  or,  which  is  the  samo 
thing,  with  the  floor  of  the  room. 

An  elegant  plate  electrical  machine  is  represented  in  the  next  figure 
(p.  83).  A  B  is  a  firm  base  of  wood,  mounted  on  castors,  so  as  to  allow 
the  machine  to  be  moved  around  easily  upon  the  floor;  CCC  the  prime 
conductor,  supported  upon  pillars  of  glass ;  P  P  two  circular  plates  of 


QUESTIONS. — 90.  Describe  the  electrical  machine.     Describe  the  large 
plate  machine. 


SOURCES    OP    ELECTRICITY. 


83 


glass  upon  the  same  axis,  and  turned  by  the  handle  H ;    R  R  R  R  the 
rubbers,  of  which  there  are  eight,  and  F  F  flaps  of  silk  to  prevent  the 


MUMEORD    3 


Electrical  Machine. 

escape  v,  f  the  fluid  before  reaching  the  point  from  the  prime  conductor. 
This  mi,-jhine,  when  put  in  proper  order,  developes  electricity  rapidly,  and 
is  decidedly  preferable  to  the  cylinder  machine. 

When  used,  the  machine  should  be  dry  and  warm,  and  per- 
fectly clean  and  free  from  dust.  Its  action  is  also  greatly  increased 
by  spreading  the  surface  of  the  rubber,  where  it  presses  against 
the  cylinder,  with  a  soft  amalgam  of  zinc,  tin,  and  mercury,  or 
with  the  yellow  sulphide  of  tin,  called  aurum  musivum,  the  latter, 
on  the  whole,  being  preferable. 


QUESTION. — What  is  the  substance  spread  over  the  rubber? 


84  SOURCES    OF    ELECTRICITY. 

To  prepare  the  amalgam,  melt  in  a  crucible  three  parts  of  zinc  and 
one  of  tin,  and,  after  removing  it  from  the  fire,  add  four  or  five  p^rts  of 
..ercury.  Stir  the  mass  with  a  stick  a  few  seconds,  and  pour  it  out 
upon  a  clear  marble  slab,  or  plate  of  metal,  and  allow  it  to  remain 
several  hours  before  breaking  it  up.  "When  wanted  for  use,  grind  it  as 
fine  as  possible  in  a  mortar,  and  mix  it  with  sufficient  tallow  to  cause  it 
to  adhere  well  to  the  rubber.  If  the  aurum  musivum  is  used,  it  is  to  be 
mixed  with  tallow  and  spread  upon  the  rubber  in  the  same  manner. 

When  the  machine  operates  properly,  if  the  knuckle  be  pre- 
sented near  the  prime  conductor,  a  vivid  spark  passes  between 
them,  and  a  slight  stinging  sensation  is  felt;  the  same  thing  also 
takes  place  on  presenting  the  knuckle  to  the  rubber,  provided  it 
be  insulated.  In  the  first  case  the  effect  is  produced  by  accu- 
mulated positive  electricity ;  in  the  second,  by  the  negative. 

91.  The  Electrophorus  (from  electron  and  phero,  I  bear)  is  an 
instrument  for  readily  obtaining  small  quantities  of  electricity. 
It  consists  of  a  plate  of  resin,  A,  about 
12  inches  in  diameter,  contained  in  a 
shallow  dish  of  metal,  and  a  metallic 
disc,  Dj  a  little  smaller  than  the  plate 
of  resin,  provided  with  a  glass  handle, 
for  removing  it  from  the  resin  at  plea- 
sure. To  operate  well,  the  surface  of 
the  resin  should  be  perfectly  smooth. 

Electrophorus.  J 

To  charge  the  electrcpnorus,  the  disc 

is  removed,  and  the  surface  of  the  resin  rubbed  briskly  with  a 
piece  of  warm,  dry  flannel,  or  'struck  several  times  with  a  dry  silk 
handkerchief,  folded  up  for  the  purpose,  by  which  a  negative 
electricity  is  excited.  If,  now,  the  disc  of  metal  be  restored  by 
means  of  its  insulating  handle,  its  lower  surface  will  become  posi- 
tive by  induction  (84),  and  its  upper  surface  negative.  By 
touching  the  upper  surface  of  the  disc,  when  in  this  position,  with 
the  finger,  the  negative  electricity  will  be  discharged ;  and  if  it  be 
then  removed  carefully  by  its  handle,  it  will  be  found  highly 
charged  with  positive  electricity,  so  that  a  considerable  spark  may 
be  obtained  from  it.  As  the  cake  of  resin  has  lost  nothing  of  its 
electricity  by  the  operation,  the  process  may  be  repeated  any 
number  of  times,  with  the  same  result. 

QUESTIONS. — How  may  a   spark   be    obtained  from    the 
91.  Describe  the  electrophorus. 


SOURCES    OF    ELECTRICITY.  85 

The  Hydro-Electric  Machine  is  an  instrument  for  exciting  elec- 
tricity by  means  of  high-pressure  steam.  The  excitement  is  attri- 
buted to  the  friction  of  the  steam,  carrying  with  it  drops  of  water, 
against  the  pipes  from  which  it  issues. 

92.  Atmospheric  Electricity. — The   general  phenomena  of 
thunder  and  lightning  are  well  known.     They  are  occasioned,  as 
Franklin  first  demonstrated,  about  a  century  ago,  by  immense 
accumulations  of  electricity  in  the  clouds,   between   which   and 
objects  upon  the   earth  violent  discharges  are  frequently  taking 
place.     The  discharge  is  believed  to  differ  in  nothing  from  the 
discharge  of  a  spark  from  the  conductor  of  an  electrical  machine, 
except  what  necessarily  results  from  the  quantity  and  intensity  of 
the  fluid  accumulated. 

Lightning -rods,  which  are  so  common  at  the  present  day,  are 
rods  of  metal  erected  upon  buildings,  extending  a  distance  above 
them  at  the  top,  and  at  the  bottom  connecting  with  the  moist 
earth.  Being  made  of  metal,  which  is  a  good  conducting  material, 
any  discharge  that  may  happen  upon  the  building  will  be  con- 
veyed by  them  without  danger  to  the  ground. 

Often  several  of  them  are  attached  to  the  same  building,  at  dif- 
ferent points,  but  they  should  always  be  connected  together,  and 
also  make  two  connections,  at  least,  with  the  moist  earth.  Any 
attempts  to  insulate  the  rod  from  the  building  are,  to  say  the 
least,  useless.  Buildings  with  tin  or  copper  roofs,  and  metallic 
water-conductors  extending  downward,  require  special  electrical 
conductors  only  for  tbe  chimneys  or  other  projecting  parts,  and 
also  from  the  water-conductors  to  the  moist  earth  below. 

Electricity  excited  by  friction  is  frequently  called  statical  elec- 
tricity, to  distinguish  it  from  dynamic  electricity,  which  will  bo 
hereafter  described,  under  the  head  of  Galvanism. 

93.  Thermo -Electricity.  —  If  a  crystal  of  tourmaline,   the 
extremities   of  which    are  dissimilar,  'is  slightly  heated   in   the 
flame  of  a  spirit-lamp,  one  end  will  be  found,  on  examination  by 
a  delicate  electrometer,  to  be  positive,  and  the  other  negative; 

QUESTIONS. — What  is  the  hydro-electric  machine  ?     92?  What  is  said 
of  lightning  and  thunder  ?     Who  first  explained  their  cause  ?     What  are 
lightning-rods  ?    What  is  said  of  buildings  with  metallic  roofs  t     93.  How 
may  crystals  sometimes  be  electrically  excited  ? 
8 


86  SOURCES    OP    ELECTRICITY. 

but  the  excitement  is  very  feeble.     Crystals  of  some  other  sub- 
stances may  be  excited  in  the  same  manner. 

But  the  more  common  method  of  exciting  electricity  by  change 
of  temperature,  is  to  heat  slightly  the  ends  of  two  or  more  small 
rods  of  different  metals  at  their  junction,  as  repre- 
sented in  the  figure.  Let  A  be  a  small  rod  of 
antimony,  and  B  another  of  bismuth,  soldered 
together  at  one  end;  and  then  let  the  heat  of  a 
spirit-lamp  be  applied,  for  a  moment,  at  the  point 
where  they  are  soldered ;  while  the  bars  are  warm- 
ing, the  bismuth  will  be  negative,  and  the  antimony 
Thermoelectricity  Positive-  The  bismuth  js  caned  the  positive,  and 
the  antimony  the  negative  metal,  because,  while 
heating,  the  positive  fluid  appears  to  originate  in  the  former,  and 
flow  to  the  latter;  but  an  electrometer  will  show  the  different 
states  of  the  metals,  as  above  indicated. 

Other  metals — and  even  non-metallic  substances — may  be  used, 
with  similar  results.  German  silver  and  brass  answer  very  well, 
the  former  corresponding  in  its  action  with  the  antimony,  and  the 
latter  with  the  bismuth. 

The  effect  will  be  considerably  increased,  if  several  pairs  of  the 
metals,  arranged  as  above,  are  associated  together,  as  shown  in 
the  accompanying  figure,  the  alternate 
rods,  A,  being  of  German  silver,  and 
the  intermediate  ones,  B,  of  brass. 
When  the  metals  are  gently  heated 
at  the  points  of  junction  at  one  ex- 

tremity of  the  bars> and  kepfc  c°o1  at 

the  other,  the  terminal  bars  become 
excited,  and  a  constant  current  flows  over  any  conducting  sub- 
stance, as  a  copper  wire,  connecting  the  extremities  of  the  series. 
If  the  upper  ends  of  the  rods  be  heated,  the  direction  of  the  cur- 
rent over  the  wire  will  be  as  shown^by  the  arrow.  If  the  lower 
ends  be  heated,  or  the  upper  ends  cooled,  its  direction  will  be 
reversed. 

QUESTIONS. — Describe  the  mode  with  two  metals.  How  may  the  effect 
be  increased  ? 


SOURCES    OP    ELECTRICITY. 


87 


Thermo-Electric  Pile. 


To  render  the  instrument  more  compact,  the  metallic 'bars  may 
be  placed  side  by  side,  with  only  a  slip  of  silk 
between  them,  the  ends  being  bent  a  little,  so 
as  to  admit  of  being  soldered  as  before.  Such 
an  instrument  constitutes  the  thermo-electric 
pile,  which  is  figured  in  the  margin,  P  and  N 
being  the  positive  and  negative  poles. 

The  existence  and  direction  of  these  cur- 
rents are  best  shown  by  a  delicate  galvanometer,  an  instrument  to 
be  hereafter  described. 

By  reversing  the  experiment,  and  passing  a  current  of  electricity 
through  the  series  of  bars,  they  will  be  heated  or  cooled,  according 
to  the  direction  in  winch  the  current  is  made  to  pass. 

94.  Chemical  Action. — Chemical  action,  as  the  solution  of  a 
metal  in  an  acid,  and  the  combustion  of  charcoal  in  an  ordinary 
fire,  it  is  believed,  is  always  attended  by  the  development  of  elec- 
tricity. In  the  combustion  of  charcoal,  the  gas  arising  from  the 
coal  is  positive,  while  the  coal  itself,  if  insulated,  is  negative;  and 
when  a  metal  is  dissolved  in  an  acid,  a  current  of  positive  electricity 
always  passes  from  the  metal  to  the  liquid,  and  any  conducting 
substance,  as  a  plate  of  copper,  contained  in  it. 

Let  Z*be  a  zinc  plate  immersed  in  water, 
acidulated  with  a  little  sulphuric  acid,  con- 
tained in  a  glass  vessel,  and  C  a  plate  of 
copper,  also  immerseU  in  the  same  liquid ; 
the  zinc  will  be  gradually  corroded,  and  a 
current  of  positive  electricity  pass  from  it 
through  the  liquid  to  the  copper;  and  if 
the  plates  are  connected  by  a  wire,  the  current. will  pass  over  it  in 
the  direction  indicated  by  the  arrows. 

But,  although  we  have,  in  these  and  other  cases  of  chemical 
action,  such  decided  and  even  powerful  developments  of  electricity, 
it  is  admitted,  that  in  very  many  cases  where  chemical  action  really 
takes  place,  no  indications  of  electricity  have  as  yet  been  observed. 
The  action  of  one  salt  upon  another,  of  one  metal  upon  another,  or 

QUESTIONS. — Describe  the  thermo-electric  pile.  94.  Is  chemical  action 
always  attended  by  the  development  of  electricity?  Describe  the  simple 
galvanic  circle.  Are  indications  of  electrical  excitement  always  observed 
during  chemical  action  ? 


Simple  Circuit. 


88 


GALVANISM. 


of  a  simple  element,  as  oxygen  or  sulphur,  upon  a  metal,  may  be 
mentioned,  as  instances  in  which  no  electrical  excitement  is  actually 
known  to  take  place. 

The  electricity  of  chemical  action,  sometimes  called  dynamical 
electricity  (92),  properly  constitutes  the  subdivision  of  the  general 
subject  of  electricity  called  GALVANISM;  and  under  this  title  it 
will  be  discussed  more  at  length,  as  it  is  this  branch  of  the  general 
subject  which  more  especially  concerns  the  student  of  chemistry. 


GALVANISM. 

95,  The  science  of  Galvanism  owes  its  name  and  origin  to  the 
experiments  on  animal  irritability  made  by  Galvani,  professor  of 
anatomy  at  Bologna,  Italy,  in  the  year  1790.  In  the  course  of 
some  of  his  investigations,  he  discovered  the  fact  that  muscular 
contractions  are  excited  in  the  leg  of  a  frog  recently  killed,  when 
two  metals,  such  as  zinc  and  silver,  one  of  which  touches  the 
crural  nerve,  and  the  other  the  muscles  to  which  it  is  distributed, 
are  brought  into  contact  with  one  another. 

The  experiment  with 'the  legs  of  a  recently  killed 
frog  is  easily  repeated,  in  the  following  manner :  — 
After  killing  the  frog,  immediately  separate  the 
hind-legs,  with  a  small  portion  of  the  spine,  and 
remove  the  skin  ;  then  bind  around  the  part  of  the 
spine  removed  with  the  legs  a  piece  of  tin-foil,  F, 
and,  holding  it  up  with  the  left  hand,  apply  a  piece 
of  .silver  coin,  or  a  rod  of  silver,  S,  bent,  if  neces- 
sary, so  that  it  shall  touch  the  tin-foil  and  the  flesh 
of  one  of  the  legs  at  the  same  time.  At  each  con- 
tact of  the  metals,,  the  muscles  of  the  leg  will  be 
violently  contracted,  and  jerking  of  the  legs  pro- 
duced. The  experiment  succeeds  best  when  the 
whole  is  kept  wet  with  clean  water.  The  irrita- 


Experlmentwith 
Frog. 


QUESTIONS. — By  what  name  is  the  electricity  of  chemical  action  gene- 
rally known?  95.  What  was  the  discovery  of  Galvani?  Describe  the 
•zperiment  v?ith  the  legs  of  the  frog. 


GALVANISM  89 

Dility  of  the  muscles  will  gradually  subside,  but  sometimes  it  will 
continue  more  than  an  hour  after  the  death  of  the  animal. 

The  large  legs  of  some  insects,  especially  those  of  the  grasshopper, 
may  be  used  for  the  same  purpose.  It 
is  necessary  only  to  remove  with  a  sharp 
penknife  a  portion  of  the  skin  from  each 
Bide  of  the  thick  part  of  one  of  the  leap- 
ing legs,  so  as  to  expose  the  flesh  ;  then 
by  laying  the  under  side  of  the  leg  upon 
a  small  piece  of  moistened  zinc,  Z,  and 

bringing  a  piece  of  copper,  C,  in  contact  Experiment  with  Grasshopper, 

with  the  flesh  exposed  on  the  upper  side, 
no  motions  will  be  observed  until  the  copper  also  touches  the  zinc,  when 
quick  movements  or  jerks  of  the  lower  part  of  the  leg,  AB,  will  be  seen, 
each  time  the  contact  is  made. 

96.  Simple  Galvanic  Circles, — A  simple  galvanic  circle  is 
formed  of  three  substances,  two  of  which  are  usually  metals, 
and  the  third  a  liquid,  as  a  dilute  acid.  The  arrangement  de- 
scribed in  paragraph  94  constitutes  such  a  circle.  The  zinc  is 
acted  upon  by  the  acid,  and  the  electrical  disturbance  takes  place 
over  all  that  part  of  its  surface  covered  with  the  liquid ;  and  a 
current  of  positive  electricity  flows  to  the  liquid.  If,  now,  a  plate 
of  copper,  or  other  metal  not  capable  of  being  acted  upon  by  the 
liquid,  be  introduced,  it  will  become  positive  by  receiving  elec- 
tricity from  the  liquid ;  and,  by4  connecting  the  two  plates  by 
wires,  a  constant  current  is  established  over  these  wires,  as  shown 
by  the  arrows.  It  matters  not,  so  far  as  galvanic  action  is  con- 
cerned, at  what  part  the  plates  touch  each  other.  .  A  current  is 
formed,  whether  contact  between  the  plates  is  made  below,  where 
covered  with  liquid,  above,  where  uncovered,  or  along  the  whole 
length  of  the  plates,  provided  both  plates  are  immersed  in  the 
same  vessel  or  diluted  acid.  But  in  every  case  /i  circuit  must  be 
formed,  around  which  the  electricity  may  traverse,  either  in  a 
single  current,  or  in  many  partial  currents,  into  which  it  ma 
divide  itself,  as  will  be  the  case  when  the  metals  are  in  contact 
along  their  whole  surfaces.  This  last  result  it  is  desirable  to 
avoid ;  and  therefore  the  metals  are  always  to  be  kept  separate 
below  the  liquid,  and  above  it  also,'  except  at  the  part  where  the 

QUESTION s. — Describe  the  experiment  with  the  leg  of  a  grasshopper. 

96.  What  constitutes  a  simple  galvanic  circle?     When  is  the  electricity 

excited  ?     What  is  the  use  of  the  plate  of  copper  ?     In  what  direction 

does  the  positive  current  flow  ?     Must  the  circuit  always  m  complete  ? 

8*  * 


GALVANISM. 


current  is  desired  to  pass.  Usually,  a  wire  is  connected  with  each 
plate,  which  may,  be  brought  in  contact  or  separated  at  pleasure. 
When  they  are  in  contact,  the  circuit  is  said  to  be  closed;  when 
they  are  separated,  it  is  said  to  be  broken,  or  open. 

97.  As  the  electricity  is  developed  entirely  by  the  chemical 
action  between  the  zinc  plate  and  the  acid,  it  is  only  upon  the 
surface  of  the  zinc  covered  by  the  acid  that  the  electric  disturbance 
takes  place ;  and,  other  things  being  equal,  the  quantity  of  elec- 
tricity set  in  motion  will  be  propor- 
tional to  the  extent  of  zinc  surface 
thus  exposed  to  the  acid.     And  in 
every  case,  in  order  to  establish  the 
current,  the  circuit  must  be  made 
complete.      Thus,  if  we  take  two 
cups  of  dilute  acid,  immersing  in  one 
a  copper,  C,  and  in  the  other  a  zinc, 
Z,  plate,  and  connect  the  two  by  a 
wire,  as  shown  in  the  figure,  though 

Borne  chemical  action  will  take  place,  no  current  will  be  established, 
for  the  reason  that  no  circuit  has  been  formed.  Chemical  action 

does  indeed  take  place  in  the  cup 
containing  the  zinc  plate,  and  its 
electricity  no  doubt  is  disturbed ; 
but,  still  no  current  can  be  esta- 
blished. For  this  it  is  necessary, 
further,  to  add  the  conducting  wire 
AB,  as  shown  in  the  next  figure; 
the  direction  of  the  current  will 
then  be  as  shown  by  the  arrows. 
It  is  to  be  understood  that  here, 
as  elsewhere,  in  using  this  lan- 
guage, we  have  reference  to  the  positive  fluid ;  but  in  reality  there 
is  just  as  much  reason  to  believe  there  is  also  at  the  same  time  a 

QUESTIONS. — When  is  the  circuit, said  to  be  closed?  When  open? 
97.  To  whsit  will  the  quantity  of  fluid  put  in  motion  be  proportional  ? 
Explain  the  necessity  of  completing  the  circuit,  as  illustrated  by  the 
figures  in  this  paragraph. 


Circuit  Complete. 


GALVANISM.  91 

negative  current  established  in  the  opposite  direction.  In  every 
case,  the  direction  of  the  positive  current  will  be  from  the,  metal 
acted  upon  to  the  liquid,  and  that  of  the  negative,  of  course,  the 
reverse.  The  direction  of  the  positive  current,  therefore,  in  the 
apparatus  last  figured,  is  from  the  zinc  cell  to  the  copper  cell,  over 
the  wire  connecting  the  cells,  and  from  the  copper  to  the  zinc  over 
the  wire  connecting  the  plates,  as  shown  in  both  cases  by  the  arrows. 
To  break  the  circuit  it  matters  not  which  of  these  wires  is  inter 
rupted ;  both  are  equally  necessary  to  complete  the  circuit. 

98.  A  simple  galvanic  circle  maybe  formed  of  one  metal  and  two  liquids, 
provided  the  liquids  are  such  that  a  stronger  chemical  action  is  induced  on 
one  side  than  on  the  other.  Nay,  even  a  plate  of  metal,  with  two  portions 
of  the  same  liquid,  may  be  made  to  constitute  the  simple  circuit,  provided 
only  the  conditions  are  such  that  one  side  of  the  metal  shall  be  acted  upon 
by  the  liquid  more  readily  than  the  other.  This  will  be  effected,  if  one 
portion  of  the  liquid  is  warmer  or  stronger  than  the  other,  or  if  one  sur- 
face of  the  metal  is  rough  and  the  other  polished. 

We  have  above  represented  the  positive  current  as  passing  from  the 
zinc,  through  the  liquid,  to  the  copper,  and  in  the  opposite  direction  over 
the  wires  connecting  the  plates  above  the  liquid ;  this  will  always  take 
place  wheri*a  diluted  acid  is  used,  which  attacks  the  zinc  more  violently 
than  it  does  the  copper ;  but  if  a  solution  of  ammonia  be  substituted  for 
the  acid,  the  copper  will  be  most  acted  upon,  and  the  current  will  move 
in  the  opposite  direction. 

It  is  not  necessary  that  copper  and  zinc  alone  should  always  be 
used  in  these  experiments;  other  metals  may  be  adopted,  with 
equal,  and,  in  some  cases,  with  even  more  decisive  resuhs.  Nor 
is  it  required  that  the  liquid  should  always  contain  an  acid ;  other 
substances,  as  solutions  of  the  salts,  are  often  very  efficacious  in 
exciting  this  subtile  fluid.  The  conditions  required  are,  that  the 
metals  and  liquid  used  should  be  such  that  chemical  action  will 
take  place  more  readily  between  one  of  them  and  the  liquid  than 
between  the  other  and  the  liquid ;  and  that  metal  is  always  found 
positive  (below  the  surface  of  the  liquid)  which  is  most  acted  upon 
by  it.  Other  things  being  equal,  the  galvanic  action  will  be  more 
intense,  the  greater  the  difference  between  the  the  two  metals 

QUESTIONS. — Is  there  a  current  of  the  negative  fluid?  What  is  its 
direction  as  compared  with  that  of  the  positive?  98.  How  may  a  simple 
circle  be  formed  of  a  single  metal  and  two  liquids  ?  Will  the  positive  current 
always  pass  from  the  zinc  to  the  copper?  Why  is  the  direction  reversed 
when  aqua  ammonia  is  used  ?  May  other  metals  besides  copper  and 
zinc  be  used  ?  What  are  the  conditions  required  ? 


92  GALVANISM. 

used,  as  regards  their  tendency  to  be  acted  on  by  the  particular 
menstruum  in  which  they  are  immersed. 

Besides  the  above  arrangement,  there  are  several  modifications 
of  the  simple  galvanic  circle,  each  possessing  its  own  peculiar 
advantages,  which  will  be  described  hereafter. 

99.  Compound  Galvanic  Circles.— Galvanic  Batteries.— The 
compound  galvanic  circle,  or  galvanic  battery,  consists  of  a  num- 
ber of  simple  circles,  so  arranged  in  a  series,  that  the  copper  of 
each  simple  circle  is  connected  with  the  zinc  of  the  one  adjacent. 
One  extreme  of  the  series,  it  will  be  evident,  will  be  copper,  and 
the  other  zinc }  they  are  often  called  the  poles  of  the  battery,  the 
former  being  positive  and  the  latter  negative. 

The  voltaic  pile  (from  the  name  of  its  inventor)  deserves  here 
to  be  noticed,  as  the  earliest  and  simplest  instru- 
ment of  this  kind,  though  by  no  means  the  most 
efficient.  It  is  formed  of  pieces  of  copper,  c,  zinc, 
z,  and  cloth,  the  latter  being  moistened  with  a  solu- 
tion of  salt  or  acidulated  water.  Commencing  with 
either  of  the  metals,  upon  this  is  placed  apiece 
of  cloth,  and  then  a  piece  of  the  other  metal ;  the 
three,  of  course,  constituting  a  simple  galvanic 
circle.  Upon  this  circle  other  simple  circles  are 
then  formed  in  the  same  manner,  care  being  taken 
to  place  the  metals  throughout  the  series  in  the 

Voltaic  Pile.  j 

same  order. 

The.  series  may  be  extended  indefinitely;  but,  usually,  from 
fifty  to  one  hundred  pairs  of  metallic  plates  will  be  found  as  many 
as  can  be  employed  advantageously.  When  in  action,  the  extreme 
zinc  plate,  which  is  represented  as  uppermost  in  the  figure,  will 
be  negative,  and  the  extreme  copper  plate  positive ;  and  if  they 
be  sonnected  by  wires,  the  current  will  flow  in  the  direction  of 
the  arrows,  both  through  the  series,  and  over  the  wires.  The 
extremes  of  the  series  are  called  its  poles,  or  electrodes  (from 
"electron)  and  odos}  a  way). 

QUESTIONS. — 99.  What  constitutes  the  galvanic  battery,  or  compound 
circle?  What  constitutes  the  poles  of  the  arrangement?  Describe  the 
voltaic  pile.  How  many  pairs  of  plates  are  needed  ?  What  are  the  poles, 
or  electrodes  ? 


GALVANISM. 


93 


Cruickshank's  Battery. 


The  voltaic  pile  is  now  rarely  employed,  because  we  possess 
other  modes  of  forming  galvanic  combinations  which  are  far  more 
powerful  and  convenient.  Cruickshank's  battery,  one  of  the  earliest 
invented,  consists  of  a  trough 
of  baked  wood,  about  thirty 
inches  long,  in  which  are  placed, 
at  equal  distances,  fifty  pairs  of 
zinc  and  copper  plates,  pre- 
viously soldered  together,  and 
so  arranged  that  the  same  metal 
shall  always  be  on  the  same  side.  Each  pair  is  fixed  in  a  groove 
cut  in  the  sides  and  bottom  of  the  box,  the  points  of  junction 
being  made  water-tight  by  cement.  The  apparatus  thus  con- 
structed is  always  ready  for  use,  and  is  brought  into  action  by 
filling  the  cells  left  between  the  pairs  of  plates  with  some  conve- 
nient solution,  which  serves  the  same  purpose  as  the  moistened 
cloth  in  the  pile  of  Volta. 

An  excellent  compound  circle,  or  battery,  is  formed  by'  com- 
bining a  number  of  cups  like  that 
represented  in  paragraph  94.  Each 
cup  contains  a  zinc,  Z,  and  copper 
plate,  C,  the  zinc  of  one  cup  being  con- 
nected with  the  copper  of  the  next, 
through  the  whole  series,  leaving  the 
two  extreme  plates  free ;  and  the  cups 
are  filled  with  diluted  acid,  or  a  solution  of  salt.  The  two  free 
plates,  constituting  the  extremities  of  the  series,  will  be  the  poles, 
or  electrodes ;  and  when  they  are  connected  by  wires,  the  current 
will  be  established  in  the  direction  of  the  arrows. 

By  studying  closely  this  arrangement,  it  will  be  seen  that  the 
actual  quantity  of  electricity  flowing  over  the  wires  connecting  the 
electrodes,  Is  no  more  than  when  a  single  cup  only,  with  a  single 
pair  of  plates,  is  used.  The  same  electrical  disturbance  takes 
place  in  each  cup,  over  the  whole  surface  of  the  zinc  plate  which 
is  covered  with  the  liquid,  the  part  of  this  plate  above  the  liquid 

QUESTIONS. — Describe  the  trough  battery.'  What  is  said  of  the  quantity 
of  electricity  flowing  in  the  compound  circle,  or  battery  ?  How  docs  this 
appear  ? 


Compound  Circuit. 


94  GALVANISM. 

becoming  negative,  and  the  liquid  becoming  equally  positive ;  the 
copper  plate  then  serves  as  a  conductor  to  take  up  this  positive 
electricity,  and  convey  it  to  the  negative  zinc  of  the  next  cup,  by 
which  it  will  be  exactly  neutralized.  However  extensive  the 
series  may  be,  this  will  take  place  with  every  alternate  zinc  and 
copper  plate  except  the  extreme  ones ;  so  that  the  quantity  pass 
ing  over  the  wires  connecting  the  electrodes,  will  be  only  that  of 
the  single  pair  of  plates  constituting  the  extremes  of  the  series. 

100.  But  although  the  quantity  of  electricity  developed  at  the 
electrodes  of  the  compound  circle  is  no  more  than  we  should 
obtain  by  using  a  single  pair  of  plates,  yet  it  will  be  found  to 
have  acquired  a  very  important  property,  called  intensity.  By 
this  term  is  meant  its  power  to  overcome  resistances  which  may 
impede  the  passage  of  the  current.  The  current  from  a  single 
pair  of  plates,  however  large  they  may  be,  will  always  be  exceed- 
ingly feeble,  and  will  not  flow  unless  the  wires  connected  with 
them  are  in  actual  contact;  but,  if  the  polar  wires  of  "the  com- 
pound circle  are  once  brought  in  contact,  they  may  be  separated 
at  a  little  distance,  and  the  current  will  continue  to  pass  between 
them,  with  a  brilliant  flame.  The  reason  is;  because  the  current 
from  the  compound  circle  possesses  sufficient  intensity  to  overcome 
the  resistance  of  the  thin  stratum  of  air  between  the  wires,  which 
is  not  the  case  with  the  current  of  the  simple  circle. 

So,  if  the  polar  wires  of  the  simple  circle  are  grasped,  one  in 
each  hand,  by  the  operator,  not  the  least  sensation  is  felt,  because 
there  is  not  sufficient  intensity  to  impel  the  current  through  the 
system,  which  is  comparatively  a  poor  conductor ;  but  if  the  same 
is  done  with  the  polar  wires  of  the  compound  circle,  especially  if 
the  series  be  extensive,  the  moment  the  circuit  is  formed,  a  pow- 
erful shock  is  experienced,  similar  to  that  received  from  the  Ley- 
den  jar.  This  is  owing  to  the  increased  intensity  of  the  current 
from  the  compound  circle,  enabling  it  to  overcome  the  resistance 
which  is  interposed. 


QUESTIONS. — 100.  What  benefit  then  is  derived  from  increasing  tho 
series  ?  What  is  meant  by  intensity  ?  Why  will  not  any  sensation  be 
produced  in  the  system  by  a  single  cell  ? 


GALVANISM.  95 

101.  From  the  above  facts  we  deduce  this  important  practical 
principle :   that,  to  produce  a  current  of  quantity,  a  single  pair 
only  of  large  plates  is  wanted;   but  to  give  intensity,  a  number 
of  simple  circles  must  be  combined,  in  the  manner  described. 

Compared  with  frictional  or  statical  electricity,  that  of  the  most 
powerful  galvanic  battery  has  always  only  a  feeble  intensity,  but 
the  quantity  is  often  immense. 

The  energy  of  any  battery,  whether  composed  of  one  or  many  simple 
circles,  will  depend  very  much  upon  the  nature  of  the  liquid  used.  A 
solution  of  common  salt,  sulphate  of  soda,  nitrate  of  potassa,  alum,  or 
other  salt,  will  answer  the  purpose,  but  acids  are  better.  Generally,  one 
of  the  stronger  acids  is  used,  diluted  with  15  or  20  times  its  weight  of 
water.  For  ordinary  purposes,  a  mixture  of  equal  parts  of  nitric  and 
sulphuric  acids,  diluted  with  20  times  their  weight  of  water,  will  be 
found  to  answer  well. 

102.  Nature  of  the  Chemical  Action  in  the  Battery. — The 

development  of  electricity  by  the  usual  galvanic  arrangements  is 
attributed  chiefly,  if  not  entirely,  to  the  decomposition  of  water 
in  contact*  with  the  zinc  plates.  Water  is  a  compound  of  oxygen 
and  hydrogen,  and  is  incapable  of  acting  upon  zinc,  unless  some 
acid  be  also  present.  But  when  a  piece  of  this  metal,  in  its  usual 
impure  state,  is  immersed  in  diluted  acid,  the  water  is  decom- 
posed, its  oxygen  combining  with  the  zinc,  forming  oxide  of  zinc, 
while  the  hydrogen  rises  in  bubbles  and  escapes  in  the  air,  and  at 
the  same  time  the  oxide  of  zinc  is  taken  up  by  the  acid.  If,  now, 
a  plate  of  copper  is  placed  in  the  diluted  acid  at  a  little  distance 
from  the  zinc,  and  the  two  connected  by  a  wire,  constituting  a 
simple  galvanic  circle  (97),  the  bubbles  of  hydrogen  will  not  rise 
around  the  zinc  as  before,  but  around  the  copper  j  showing  that 
the  gas  has  in  some  way  been  transmitted  through  the  liquid 
between  the  plates,  though  not  the  least  appearance  of  any  motion 
can  be  observed  by  the  eye.  If  the  connecting  wire  is  removed, 
the  evolution  of  hydrogen  at  the  copper  plate  at  once  ceases  with 
the  cessation  of  the  electrical  current,  but  continues  to  rise  slowly 

QUESTIONS. — 101.  "What  is  said  of  the  intensity  of  the  excitement  pro- 
duced by  the  galvanic  battery,  as  compared  with  that  of  statical  electricity  ? 
What  acids  are  recommended  for  use  in  the  battery  ?  102.  What  is  said 
of  the  chemical  action  that  takes  place  when  a  piece  of  zinc  is  immersed 
in  a  dilute  acid  ?  What  is  the  occasion  of  the  bubbles  upon  the  zinc  ? 
When  a  copper  plate  is  connected  with  the  zinc  where  do  the  bubbles  of 
hydrogen  make  their  appearance? 


9t> 


GALVANISM. 


around  the  zinc.  This  latter  effect,  however,  is  occasioned  by  tha 
impurity  of  the  zinc.  Thus  it  would  seem  that  the  development 
of  the  current  is  occasioned  entirely  by  the  decomposition  of  the 
water,  and  the  formation  of  oxide  of  zinc. 

When  the  battery  is  in  active  operation,  though  the  hydrogen 
is  rapidly  evolved  at  the  copper  plates,  yet  the  whole  surfaces  of 
these  plates  will  be  all  the  time  covered  with  a  film  of  this  gas> 
which  interferes  with  its  conducting  power,  and  prevents  the  fret 
passage  of  the  current;  at  the  same  time,  as  a  matter  of  course, 
diminishing  very  considerably  the  energy  of  the  battery.  T& 
remedy  this  difficulty,  several  new  forms  of  the  battery  have 
recently  been  invented,  which  act  with  great  energy,  and  will 
here  be  briefly  described. 

103.  Daniel's  Constant  Battery.— This  excellent  instrument 
consists  of  a  cylindrical  vessel  of  copper,  C,  in 
which  is  placed  another  smaller  one,  L,  made  of 
unoiled  leather,  or  ungjazcd  porcelain,  through 
which  water  will  gradually  percolate;  and  in  the 
latter  is  contained  a  rod  of  zinc,  Z,  about  an  inch 
in  diameter.  To  charge  it,  the  inner  porous  ves- 
sel, which  contains  the  rod  of  zinc,  is  filled  with 
diluted  sulphuric  acid  (acid  1  part,  and  water  8 
parts),  and  the  space  around  the  inner  vessel  with 
a  saturated  solution  of  blue  vitriol,  acidulated  with 
sulphuric  acid.  To  the  side  of  the  copper  vessel, 
and  also  to  the  zinc  rod,  wires  are  soldered,  with 
binding  screws  for  holding  the  polar  wires;  the  one  connected 
with  the  copper  being  positive,  and  the  other  negative,  as  shown 
by  the  algebraic  signs. 

Usually,  the  zinc  rod  is  amalgamated  with  mercury,  which  is 
done  by  rubbing  the  surface  with  mercury,  while  covered  with 
some  weak  acid.  This  renders  the  chemical  action  over  the  whole 
surface  more  uniform,  and  the  action  of  the  battery  more  constant; 
but  the  same  thing  may  be  accomplished  with  less  trouble,  by 
using  the  zinc  in  its  ordinary  state,  and  substituting,  in  the  porous 


Daniel's  Cell. 


QUESTIONS.— 103.   Describe  Daniel's  battery.     How  is  the  zinc  amal- 


GALVANISM.  97 

cell,  a  saturated  solution  of  sulphate  of  soda  (Glauber's  salt),  instead 
of  the  diluted  acid. 

The  above  arrangement,  it  is  plain,  constitutes  a  simple  galvanic 
circle  j  and  its  action  is  particularly  energetic  and  constant,  in 
consequence  of  the  accumulation  of  hydrogen  gas  upon  the  copper 
plate  (102)  being  completely  avoided.  This  will  appear  from  th'j 
following  explanation.  ^ 

In  this  instrument,  as  in  the  more  common  one  first  described^ 
the  electricity  is  developed  at  the  surface  of  the  zinc,  by  the  decom- 
position of  the  water;  the  oxygen  combining  with  the  zinc,  and 
the  hydrogen  passing  through  the  porous  vessel  into  the  vitriol 
solution,  and  thence  to  the  sides  of  the  copper  vessel,  which  con- 
stitutes the  copper  plate  of  the  series  (98).  Here  the  hydrogen 
does  not  make  its  appearance  in  bubbles  upon  the  surface  of  the 
copper,  as  in  the  common  arrangement,'  but  enters  into  a  new 
combination  with  the  oxygen  of  the  oxide  of  copper  deposited 
from  the  vitriol  solution.  Blue  vitriol  is  a  jcompound  of  sulphuric 
acid  and  oxide  of  copper;  and  while  the  battery  is  in  operation, 
it  is  all  the  time  decomposing,  its  acid  passing  into  the  pocous 
cup,  to  act  upon  the  zinc,  while  the  oxide  of  copper  is  itself  also 
decomposed,  its  oxygen  combining  with  the  hydrogen  at  the  sur- 
face of  the  outer  vessel,  which  receives  a  new  coating  of  metallic 
copper. 

Any  number  of  these  arrangements  may  be  united,  by  connecting  the 
zinc  of  one  with  the  copper  of  the  next,  as  heretofore  Described  (99); 
and  a  battery  so  constructed  has  this 
great  advantage,  that  no  action  takes 
place  when  the  circuit  is  not  closed. 
It  is  also  very  constant  in  its  action, 
affording  a  uniform  current  for  seve- 
ral hours  in  succession. 

The  figure  in  the  margin  repre- 
sents a  battery  of  this  kind,  of  six 
series. 

When  a'battery  of  this  kind  is  to 
be  used  some  time,  a  quantity  of  un- 
dissolved  blue  vitriol  should  be  kept 

in  the  upper  part  of  the  copper  cell,  Daniel's  Battery, 

either  upon  a  shelf  provided  for  the 
purpose,  or  in  a  muslin  bag,  to  keep  the  solution  constantly  saturated 

QUESTIONS. — How  is  the  hydrogen  disposed  of  in  this  arrangement? 
Why  is  it  called  a  constant  battery  ?     How  are  the  separate  cells  to  be 
united  to  form  the  compound  arrangement? 
0 


98 


GALVANISM. 


Grove's  Cell. 


104.  Grove's  Cell. — This  battery,  invented,  by  Professor  Grove, 
of  London,  is  remarkable,  not  only  for  the  constancy  of  its  action, 
but  also  for  its  great  intensity. 

The  construction  of  this  battery  is  shown  in  the  accompanying 
figure.  A  glass  or  porcelain  cup,  of  a  proper 
•*•  ~~^  size,  is  used,  and  in  it  is  placed  a  hollow  cylinder 
of  zinc,  Z^.(usually  having  a  slit  in  one  side,  to 
allow  a  free  passage  to  the  liquid),  and  insi  le 
of  this,  a  small  cylindrical  cup,  C,  of  porous  or 
unglazed  porcelain.  The  glass  cup  is  then  filled 
with  diluted  sulphuric  acid  (of  the  same  strength 
as  is  used  in  Daniel's  battery),  and  the  porous 
cup  with  strong  aquafortis  (nitric  acid).  Lastly, 
a  thin  slip  of  platinum,  P,  is  suspended  in  the 
aquafortis,  and  supported  by  a  piece  of  wood 
attached  to  the  side  of  the  glass  cup,  through 
which  a  wire  passes,  and  is  bent  in  the  form  represented  in  the 
figure.  A  projection  upward  from  the  zinc  supports  a  binding 
screw,  shown  on  the  right,  and  another  is  soldered  to  the  wire  to 
which  the  platinum  is  attached,  shown  at  the  left.  These,  of 
course,  serve  as  the  positive  and  negative  poles  of  the  circle ;  and 
to  them  the  polar  wires  may  be  attached,  when  required. 

The  zinc  should  be  well  amalgamated,  as  heretofore  described. 
The  action  of  this  battery  is  essentially  the  same  as  that  of 
Daniel's,  except  that  the  hydrogen  from  the  decomposition  of  the 
water,  passing  into  the  porous  cell,  is  expended  in  decomposing 
the  nitric  acid,  which,  when  the  instrument  is  in  action,  gives 
off  copious  nitrous  fumes.  To  understand  this,  it  is  necessary  to 
recollect  that  nitric  acid  is  a  compound  of  nitrogen  and  oxygen ; 
and  the  hydrogen  entering  the  porous  cell  takes  away  a  part  of  it»s 
oxygen,  forming  water;  and  the  binoxide  of  nitrogen  which  is 
liberated  rises,  and  uniting  with  more  oxygen  from  the  air,  forms 
*he  nitrous  fumes. 

A  battery  of  twelve  series  of  Grove's  arrangement  is  represented  in 
the  following  figure.  The  cups  are  contained  in  a  box  of  wood,  for  the 
sake  of  convenience  in  handling,  and  between  the  cups  are  partitions  to 


QUESTIONS. — 104.  Describe  Grove's  cell    What  in  this  case  becomes  of 
the  hydrogen  ? 


GALVANISM. 


hold  them  more  steadily.     The  hollow  cylinders  of  zinc,  when  made  for 
this  purpose,  are  oast  with 'arms  rising  from  one  side,  and  then  project- 


Grove's  Battery. 

• 

ing  a  distance  horizontally;  -and  to  the  end  the  platinum  plate  is  firmly 
soldered,  so  as  to  hang  directly  in  the  nitric  acid  cup  of  the  next  adjacent 
series.  The  whole,  it  will  be  observed,  forms  a  connected  series ;  and 
the  terminal  zinc  at  one  extremity,  and  the  platinum  at  the  other,  with 
each  of  which  a  binding  screw  is  connected,  constitute  the  negative  and 
positive  poles.  The  terminal  platinum  plate  is  supported  in  its  place  by 
a  wire  passing  through  a  piece  of  wood  attached  to  the  side  of  the  box 
or  the  cup,  as  represented  in  the  figure.  When  a  greater  power  is 
required  than  is  afforded  by  a  battery  of  this  size,  it  is  found  more  con- 
venient to  connect  two  or  more  batteries  together  than  to  have  a  larger 
number  united  in  one  series.  The  Batteries  are  connected  by  extending 
a  wire  from  the  positive  pole  of  one  to  the  negative  of  the  next ;  they 
then  in  reality  become  a  single*series. 

This  is  the  kind  of  battery  generally  used  in  working  the  magnetic 
telegraph,  as  it  excels  all  others  in  the  constancy  and  intensity  of  its 
action. 

105.  Smee's  Cell, — This  very  efficient  arrange- 
ment is  represented  in  the  figure  in  the  mar- 
gin. Two  plates  of  zinc,  well  amalgamated, 
are  firmly  held  together  against  a  piece  of  wood, 
W,  by  means  of  a  brass  clamp  and  screw;  and 
between  them  is  a  plate  of  silver,  S,  the  surface 
of  which  has  been  coated  over  with  metallic 
platinum,  in  a  state  of  fine  powder,  called  plati- 
num black.  The  zinc  and  silver  plates  are  then 
suspended  in  a  glass  vessel,  the  piece  of  wood 
resting  upon  the  top.  A  binding  screw,  con- 
stituting the  -f-  pole,  is  connected  by  a  wire 


QUESTIONS.— What  is  said  of  the  character  of  batteries  of  this  kind  t 
t05.  Inscribe  Sm&a  arrangement. 


100  G  A  L  V  A  X  ISM. 

(which  is  insulated  from  the  brass  clamp  through  which  it  passes) 
with  the  silver  .plate,  and  another,  constituting  the  —  pole,  is 
soldered  to  the  clamp  which  holds  the  zinc  plates  in  their  places. 
The  liquid  used  in  the  glass  cup  is  sulphuric  acid,  diluted  with- 
10  or  15  times  its  weight  of  water. 

The  peculiar  advantage  possessed  by  this  form  of  the  batter} 
depends  upon  the  rapid  evolution  of  hydrogen  from  the  platinized 
silver  plate.  We  have  seen  above  (102)  that  the  accumulation  of 
this  gas  upon  the  smooth  surface  of  the  copper  plate,  in  the  old 
arrangement,  considerably  retards  the  passage  of  the  electric  cur- 
rent, by  preventing  the  liquid  in  a  measure  from  coming  in  contact 
with  the  plate;  but  this  is  avoided,  in  Smee's  arrangement,  by 
the  roughened  surface  of  the  silver  plate,  produced  by  the  platinum 
deposit. 

Compound  circles  or  batteries  are  readily  formed  by  combining  the 
simple  series  of  Daniel  "with  each  other,  or  those  of  Smee  with  each  other; 
but  the  proper  mode  of  doing  it  will  be  easily  understood  without  further 
illustrations.  For  many  purposes,  they  answer  well ;  but  neither  of  them 
possesses  the  energy  of  that  of  Grove  above  described. 

As  batteries  are  sometimes  constructed,  and  as  they  are  usually  repre- 
sented in  books,  the  direction  of  the  current  appears  to  be  the  reverse 
of  that  in  the  simple  circuit,  but  this  is  in  consequence  of  there  being  a 
superfluous  plate  at  each  extremity  whfbh  serves  only  as  a  conductor. 
In  the  figures  in  this  book,  however,  these  superfluous  plates  are  not 
represented,  and  the  remarks  in  the  text  are  made  with  reference  to 
instruments  of  this  construction. 

106.  Bunsen's  arrangement  is  constructed  on  the  same  principle  as 
Grove's,  except  that  hollow  cylinders  of  carbon  surrounding  the  zinc, 
are  substituted  instead  of  the  platinum  plates.  The  carbon  cylinders 
are  made  of  carbon  from  gas-retorte,  by  grinding  it  to  a  powder,  and 
then  kneading  it  with  flour  dough,  and  afterwards  baking  it  in  a  strong 
heat. 

107.  Ohm's  Formula. — The  effective  force  of  a  battery  of 
any  construction  will  depend  upon  a  number  of  conditions,  or 
circumstances,  which  are  well  expressed  in  a  formula  devised  by 
Prof.  Ohm,  and  therefore  generally  known  by  his  name. 

To  estimate  the  effective  force  of  any  galvanic  arrangement,  two 
t^ngs  are  to  be  considered,  viz  :  1.  The  electromotive  force,  or 
absolute  tension  of  the  electric  fluid,  and  2.  The  resistance  to  be 
overcome.  As  there  must  always  be  some  resistance  to  the  passage 

QUESTION. — What  is  the  peculiar  advantage  of  Smee's  arrangement? 
106.  Describe  Bunseri's  arrangement.  107.  What  is  the  design  of  Glint1* 
formula?  To  estimate  the  effective  force  of  a  battery  what  two  things 
must  be  considered  ? 


GALVANISM.  101 

of  the  fluid,  the  effective  force  must  always  be  less  than  the  full 
electromotive  power,  if  such  resistance  did  not  exist.  The  resist- 
ance will  be  occasioned  chiefly  by  the  wires  connecting  the  poles, 
but  something  is  due  also  to  the  liquid  between  the  plates. 

'  In  the  case  of  a  single  cell,  let  the  absolute  tension  be  repre- 
sented by  t,  and  let  r  be  the  resistance  of  the  wire,  and  /  the 
resistance  of  the  liquid  between  the  plates,  and  A  the  effective 
force;  then  will  A  =  —  —,.  That  is,  the  effective  power  of  the 
cell  will  be  directly  proportional  to  the  absolute  tension  of  the 
electric  fluid,  which  will  in  general  depend  upon  the  activity  of 
the  chemical  action  taking  place,  and  inversely  as  the  sum  of  the 
resistances  of  the  liquid  between  the  plates,  and  that  of  the  con- 
ducting wire. 

To  apply  the  same  law  in  the  case  of  a  compound  series  or 
battery,  we  have  the  following  formula  :  A  =  <nrn  in  which  n  is 
used  to  represent  the  whole  number  of  cells.  We  see,  therefore, 
that  the  effective  power  will  be  directly  proportional  to  the  elec- 
tromotive force  of  each  cell,  multiplied  by  the  number  of  cells, 
and  inversely  as  the  resistance,  which  is  made  up  of  the  resistance 
of  the  wire  connecting  the  poles,  and  the  resistance  of  the  fluid 
of  the  cells. 

The  resistance  r  will  be  proportional  to  the  length  of  the  wire 
and  inversely  as  tbe  area  of  its  section.  The  resistance  /  will  be 
proportional  to  the  thickness  of  the  stratum  of  liquid,  and  inversely 
as  its  conducting  power. 

103,  Animal  Electricity. — Several  animals,  .as  the  gymnotu* 
electricus,  which  is  found  in  the  fresh  waters  of  some  parts  of 
South  America,  'the  silurus  electricus,  found  in  some  African 
rivers,  and  the  torpedo,  a  species  of  which  has  been  taken,  though 
rarely,  upon  the  sea-coast  of  Massachusetts,  possess  the  power  of 
giving  strong  shocks  of  electricity,  by  means  of  peculiar  galvanic 
arrangements  .with  which  nature  has  provided  them. 

The  electrical  apparatus  of  these  animals  is  plainly  connoted 
with  the  nervous  system,  and  is  perfectly  under,  the  animal's  con- 

QUESTIONS. — That  resistance  will  there  always  be  to  the  passage  of 
the  current?     To  what  is  the  effective  force  of  a  battery  proportional? 
108.  What  animals  are  mentioned  as  possessing  the  power  of  giving  shocks 
of  electricity ".     Is  their  electrical  apparatus  under  control  of  the  will  ? 
9* 


102        EFFECTS    OF    GALVANIC    ELECTRICITY. 

trol.  It  is  made  use  of  as  a  defence  against  enemies,  and  in 
paralyzing  other  small  fishes,  which  are  immediately  seized  for 
food.  The  shock  given  by  some  of  these  animals  is  very  powerful. 


EFFECTS    OF    GALVANIC    ELECTRICITY. 

109.  Galvanic  electricity,  as  we  have  seen,  differs  essentially 
from  ordinary,  or  statical  electricity,  in  several  important  particu- 
lars, as  its  feeble  intensity,  its  immense  quantity,  and  its  flowing 
in  a  continuous  current ;  and,  as  we  should  expect,  there  is  a  cor- 
responding difference  in  the  effects  which  these  two  kinds  of 
electricity  are  capable  of  producing. 

In  consequence  of  the  feeble  intensity  of  the  most  powerful 
galvanic  battery,  it  is  quite  incapable  of  producing  many  of  the 
more  brilliant  effects  of  the  common  electrical  machine,  but  others 
are  produced  not  less  important.  In  fact,  in  the  galvanic  battery 
the. ordinary  signs  of  electrical  excitement  are  almost  wholly  want- 
ing, plainly  for  the  reason  that  these  indications  depend  chiefly 
upon  intensity.  Thus,  when  the  circuit  of  a  powerful  battery  is 
broken,  that  is,  when  the  poles  or  electrodes  are  disconnected, 
both  of  them  give  signs  of  electrical  excitement,  if  examined  by 
the  ordinary  tests;  one  of  them  being  positive,  and  the  other 
negative,  as  before  explained;  but  the  indications  are  exceedingly 
feeble. 

A  Leyden  vial  may  also  be  charged  by  establishing  a  communi- 
cation between  one  of  its  surfaces  and  one  of  the  electrodes,  while 
the  other  surface  is  connected  with  the  other  electrode ;  but  the 
charge  will  always  be  slight. 

Either  of  the  electrodes  will  give  a  spark  to  a  conductor  pre- 
sented to  it,  but  it  is  shown  best  by  bringing  the  two  polar  wires 
in  close  proximity;  and  on  establishing  the  communication  be- 
t^en  the  electrodes  by  the  hands,  previously  moistened,  a 
p  werful  shock  is  felt,  precisely  like  that  produced  by  the 

QUESTIONS. — 109.  In  what  respect  does  galvanic  differ  from  Statical 
electricity  ?  In  the  charged  galvanic  battery,  nre  the  ordinary  signs  of 
electrical  excitement  apparent?  May  the  Leyden  vial  be  charged  by  an 
active  battery  ?  How  may  a  spark  be  obtained  from  one  of  the  elec- 
trodes? How  ia  the  shock  produced? 


EFFECTS     OF    GALVANIC    JSLECTRIOITY.        103 

discharge  of  the  Leyden  jar.  But  the  shock  is  felt  only  at  the 
moment  the  current  is  established  ;  if  afterwards  the  hands  be  held 
firmly  in  their  places  a  peculiar  feeling  of  numbness  in  the  muscles 
in  the  line  of  the  current  succeeds,  and  continues  until  the  current 
is  again  broken. 

110,  Heating  Effects — Deflagration. — When  the  communica- 
tion between  the  electrodes  of  an  active  battery  is  established  by 
various  substances  capable  of  conducting  the  current,  they  often 
become  intensely  heated,  and  sometimes  even  consumed  or  dissi- 
pated in  vapor  by  the  heat.  Thus  a  small  wire  interposed  in  the 
circuit  will  become  red-hot  in  an  instant,  and  gold  and  silver  leaf, 
in  the  same  circumstances,  will  take  fire  and  burn  with  brilliant 
scintillations. 

This  heating  effect  of  the  galvanic  current  may  be  produced  at 
a  distance  from  the  battery,  and  gun-powder  or  gun-cotton  and 
other  combustibles  ignited.  Let  W  be  two 
copper  wires,  coated  with  tarred  twine,  so  as 
to  insulate  them  perfectly,  having  their  ex- 
tremities connected  by  a  very  small  platinum 
wire  soldered  to  them,  as  shown  through  the 
glass  cup  C.  Let  the  cup 
be  now  filled  with  gunpow- 
der 01  gun-cotton,  and  the 
other  ends  of  the  wires 
brought  in  contact  with  the  Gunpowder  Exploded, 

poles  of  the  battery;  immediately  on  the  passage  of  the  current, 
the  platinum  wire  will  be  heated,  and  the  powder  exploded.  The 
wires,  if  well  coated,  may  be  extended  under  water,  and  a  sub- 
marine magazine  exploded.  This  method  has  been  used  for 
exploding  the  powder  in  the  blasting  of  rocks. 

A  mixture  of  oxygen  and  hydrogen  may  be  inflamed  in  the 
same  manner;  for  this  purpose  the  mixed  gases  are  contained  in 
a  pistol,  into  which  the  wires  are  inserted,  as  shown  in  the  figure 
on  p.  104. 

QUESTIONS.  —  Does  the  shock  continue  while  the  current  flows  ? 
110.  How  may  the.  heating  effects  of  the  current  be  shown?  How 
may  gunpowder  be  inflamed?  Describe  the  method  of  exploding  a 
mixture  of  oxygen  and  hydrogen. 


104        EFFECTS    OP    GALTANIC    ELECTRICITY. 


Pistol. 

When  pieces  of  well-burnt  charcoal  are  attached  to  the  polar 
wires,  on  bringing  them  near  each  other,  a  most  brilliant  arc  of 

flame  appears  between  them,  and  the 
points  appear  to  be  vividly  ignited,  as 
Charcoal  Points.  jf  heated  by  any  other  means.     But 

the  heating  effect  does  not  depend  upon  the  combustion  of  the 
coal,  since  it  is  equally  as  great  when  the  charcoal  points  are 
excluded  from  the  air.  To  produce  the  effect,  the 
points  must  first  be  brought  into  contact,  but  they 
may  afterwards  be  separated  some  distance,  and  the 
arc  of  flame  will  continue.  At  the  same  time  a  por- 
tion  of  the  carbon  point  in  connection  with  the  positive 
pole  disappears,  and  the  other  point  is  elongated  as  if 
by  matter  transferred  from  the  other  side.  If  the  char- 
coal connected  with  the  positive  pole  be  hollowed  out  so 
MetaTvoia-  as  to  receive  pieces  of  metal,  as  silver,  gold,  or  platinum, 
taiized.  when  the  current  passes  the  metals  will  not  only  be 
fused,  but  appear  to  be  even  volatilized,  and  pass  off  in  fames. 

111.  Chemical  Effects,  Decomposition. — The  chemicS^  effects 

,of  the  galvanic  current  are  seen  chiefly  in  the  decomposition  of 

compound  substances,  and  in  the  operations  of  electro-metallurgy, 

soon  to  be  explained.     Thus,  when  two  gold  or  platinum  wires 

QUESTIONS. — Describe  the  experiment  with  the  charcoal  points.  How 
may  the  metals,  as  gold  and  platinum,  be  even  volatilized?  111.  In 
what  are  the  chemical. effects  of  galvanism  chiefly  seen? 


EFFECTS    OF    GALVANIC    ELECTRICITY.        105 


Decomposition  of  Water. 


are  connected  with   the   opposite  ends 

of  a  battery,  and  their  free  extremities 

are    plunged    into    the    same    cup    of 

water,    but     without     touching     each 

other,  hydrogen   gas  is  disengaged   at 

the  negative,  and  oxygen  at  the  positive 

wire,   these   being,  as   we   have    seen 

(102),  the  elements  of  water.     If  the 

wires  are  brought  into  actual  contact 

in  the  water  the  current  is  conducted 

directly  through   without  acting  upon 

the  water,  and  if  any  other  metal  except 

gold  or  platinum  is  used  for  the  posi- 
tive pole,  it  will  be  rapidly  attacked  by 

the  liberated  oxygen. 

By  using  one  or  the  other  of  the 

two  pieces  of  apparatus  figured  in  the 

margin,  the  oxygen  and  hydrogen  may 

be  collected  separately  or  together,  as 

may  be  desired.     The  first  piece  consists  of  an  open  vessel,  with 

a   shelf   and    support   for   two    tubes, 

N  and  P,  which  are  closed  at  the  top, 

and  binding  screws  marked  +  and  — 

which  connect  with  wires  passing  un- 
derneath   the   edge   of   the  glass,   and 

terminating  in  the  mouths  of  the  tubes. 

After  filling  the   tubes  and   inserting 

them  in  their  places, — the  vessel  being 

previously  nearly  filled  with  water,  the 

current  from  the  battery  is  made  to  pass 

through   in  the   ordinary  way.      Very 

soon  the  gases  will  be  seen  to  collect  in 

the   tubes;    and  as  water  contains  by          Decomposition  of  water. 

volume   twice  as  much   hydrogen  as  oxygen,  the  tube  N  COD- 
QUESTIONS. — How  may  water  be  decomposed  by  the  current  ?     Describe 

the  apparatus  for  decomposing  water  and  collecting  the  gases  formed  in 

separate  tubes.     Describe  that  for  collecting  the  gases  together. 


100       EFFECTS    OF    GALVANIC    ELECTRICITY. 

taining  it  will  be  found  to  fill  proportionally  faster  than  tho 
other. 

When  the  two  wires  terminate  in  the  same  tube,  the  two  gases 
will  be  collected  together;  and  by  passing  afterwards  a  spark  of 
common  electricity  through  the  mixture  they  will  be  again  united, 
with  an  explosion. 

In  decomposing  water,  it  is  well  always  to  add  a  few  drops  of 
oil  of  vitriol,  to  increase  its  conducting  power. 

If  other  compound  bodies,  such  as  some  acids  and  solutions  of 
salts,  are  exposed  to  the  action  of  galvanism,  they  are  also  decom- 
posed, one  of  their  elements  appearing  at  one  electrode,  and  the 
other  at  the  other.  An  exact  uniformity  in  the  circumstances 
attending  the  decomposition  is  also  remarked.  Thus,  in  decom- 
posing water  or  other  compounds,  the  same  kind  of  body  is  always 
disengaged  at  the  same  side  of  the  battery.  The  metals,  inflam- 
mable substances  in  general,  the  alkalies,  earths,  and  the  oxides 
of  the  common  metals,  are  found  at  the  negative  electrode ;  while 
oxygen,  chlorine,  and  the  acids,  go  over  to  th.e  positive  electrode. 

112.  Those  substances  which  appear  at  the  positive  side  have 
been  called  electro-negative  bodies,  while  those  that  are  separated 
at  the  negative,wire  are  called  electro-positive  bodies. 

The  decomposition  of  a  salt,  which  must  be  in  solution,  may  be 
shown  in  the  following  manner : — Let  two  wine-glasses  be  filled 
with  a  solution  of  sulphate  of  soda,  (which 
is  a  compound  of  sulphuric  acid  and  soda,) 
and  let  some  fibre's  of  moistened  cotton  be' 
extended  between  them,  as  shown  in  the 
figure.  If  the  current  is  then  transmitted 

tionofSalt.         through     tbe    cups?     the     3&It    wi]1     goon     bQ 

decomposed,  and  the  cup  in  conneotion  with'fhe  positive  electrode 
will  be  found  to  contain  weak  sulphuric  acid,  and  that  in  con- 
nection with  the  negative  electrode  a  solution  of  soda.  If,  now, 
a  little  red  cabbage-water  be  poured  into  each,  the  acid  liquid  will 
become  red,  and  the  soda  solution  green. 

QUESTIONS. — May  other  compounds  also  be  decomposed  ?  In  de- 
composing a  compound,  will  the  same  element  always  appear  at  the 
game  electrode?  112.  What  are  electro-negative  and  electro-positive 
substances  ? 


EFFECTS    OF    GALVANIC    ELECTRICITY.       107 

A  compound  to  be  decomposed  by  the  current  must  be  in  the 
i'iquid  state,  and  must  of  course  be  a  conductor;  but  all  com- 
pounds answering  these  conditions  are  not  by  this  means  capable 
of  direct  decomposition.  Yet  compounds,  not  directly  decom- 
posable by  the  current,  are  often  decomposed  indirectly  by  the 
hydrogen  derived  from  the  decomposition  of  water  that  is  present. 
Thus,  sulphuric  acid  is  not  directly  decomposed  by  the  current, 
but  hydrogen  separated  from  the  water  present,  making  its  appear- 
ance at  the  negative  pole,  unites  with  the  oxygen  of  the  acid,  and 
causes  the  evolution  of  fumes  of  sulphuric  acid. 

Following  the  suggestions  of  Faraday,  the  term  electrolysis 
(from  electron,  and  luo,  I  unloose)  is  now  very  generally  used 
to  express  this  electro-chemical  decomposition  ',  and  the  term 
electrolyte  to  indicate  a  compound  capable  of  being  thus  decom- 
posed. The  positive  pole  or  electrode  is  also  called  the  anode, 
and  the  negative  pole  the  cathode  (from  ana,  upward,  Jcata, 
downward,  and  odos,  a  way). 

But  instead  of  the  terms  anode  and  cathode,  most  writers  prefer 
to  say  positive  or  negative  electrode,  as  the  case  may  be. 

The  elements  of  a  compound  capable  of  separation  by  this 
mode,  are  termed  ions  (from  the  Greek  participle  ion,  going) ; 
the  anion  being  the  element  which  appears  at  the  anode,  and  the 
cation  the  element  which  goes  to  the  cathode.  It  will  at  once  be 
seen  that  the  anions  are  electro-negatives,  and  the  cations  electro- 
positives. 

It  is  not  to  be  inferred  from  the  above  remarks,  that  every  sub- 
stance will  always  make  its  appearance  at  the  same  electrode, 
whatever  may  be  the  other  substance  from  which  it  is  separated 
by  the  electrolytic  action.  Oxygen  does  indeed  always  appear  at 
the  positive  electrode,  and  potassium  at  the  negative  j  but  in  the 
electrolyses  of  the  compounds  of  other  substances,  that  element 
will  appear'at  the  positive  electrode  which  is  most  electro-negative, 
and  that  at  the  negative  which  is.most  positive. 

113.  The  following  table  exhibits  the  electrical  relations  of  several  of 
the  more  important  elements.  .It  is  to  be  understood  that  each  sub- 

QUESTIONS. — Are  all  compounds  directly  decomposable  by  the  current? 
Define  the  terms,  electrolyte,  anode  and  cathode.  What  are  ions  ? — what 
anions  and  cations  ?  Will  every  substance  always  make  its  appearance 
at  the  same  electrode,  whatever  may  be  the  other  from  which  it  is  sepa- 
rated? What  is  the  law  in  this  respect? 


108        EFFECTS    OF    GALVANIC    ELECTRICITY. 

stance  in  the  first  column  is  electro-negative  as  compared  -with  each  ono 
below  it,  but  in  the  second  column  each  substance  is  negative  as  com* 
pared  with  all  above  it: 


Oxygen. 

Fluorine. 

Chlorine. 

Iodine. 

Sulphur. 

Nitrogen. 

Phosphorus. 

Arsenic. 

Antimony. 

Gold. 

Mercury. 

Silver. 


Potassium. 

Sodium. 

Calcium. 

Carbon. 

Hydrogen. 

Zinc. 

Iron. 

Bismuth. 

Tin. 

Lend. 

Copper. 

Silver. 


114,  We  have  seen  that  the  decomposition  of  a  compound  takes 
place  only  when  the  current  is  made  to  pass  through  it — then  one 
of  the  ingredients  is  collected  at  one  electrode,  and  the  other  at 
the  other  electrode ;  thus  in  the  electrolysis  of  water,  the  oxygen 
is  collected  at  the  positive  and  the  hydrogen  at  the  negative  elec- 
trode. But  how  is  it  that  these  effects  are  produced  ?  and  at  what 
precise  point  or  points  ?  Are  both  gases  liberated  at  each  elec- 
trode, but  one  only,  hydrogen  (the  electro-positive  element),  col- 
lecting at  the  negative  electrode,  and  the  other,  oxygen  (the 
electro-negative  element),  collecting  at  the  positive  pole?  This 
would  require  that  opposite  currents  of  oxygen  and  hydrogen 
should  be  passing  by  each  other  in  the  liquid  between  the  poles 
while  the  battery  is  in  operation,  of  which  we  have  no  evidence. 
Or,  does  the  decomposition  take  place  along  the  whole  line  be- 
tween the  poles  traversed  by  the  current  ?  Other  similar  inquiries 
may  be  made,  which  cannot  be  answered  positively,  but  the  fol- 
lowing is  believed  to  be  a  correct  representation  of  the  phenomena 
witnessed,  so  far  as  we  are  able  to  determine.  Water  is  a  com- 
pound of  hydrogen,  which  we  will  represent  by  II,  and  oxygen, 
which  we  will  indicate  by  0; — and  the  compound  by  Jf.  A  tier 
or  row  of  particles  between  the  "poles  we  may  then  represent  thus : 

H,  H,  H,  H,  II,  H  — 
+  000000 

QUESTIONS. — 114.  When  only  does  the  decomposition  of  a  compound 
take  place?  Describe  the  manner  in  which  the  decomposition  of  water 
is  supposed  to  be  effected  by  the  passage  of  the  electric  current. 


EFFECTS    OF    GALVANIC    ELECTRICITY.        109 

the  sign  -f  indicating  the  position  of  the  positive  pole,  and  —  that 
of  the  negative. 

Instantly  as  the  current  begins  to  pass,  oxygen  from  the  decom- 
position of  the  water  appears  on  the  positive  side,  and  hydrogen 
from  the  same  decomposition  at  the  negative  side,  a  state  of  things 
which  may  be  represented  as  follows : 

,  H,  n,  rl,  H,  H,  H  — 

+  000000 

"We  have  now  one  less  pa'rticle  of  water  than  before,  and  one  of 
the  elements  of  the  decomposed  particle  is  found  at  one  electrode, 
and  the  other  at  the  other  electrode.  To  produce  this  effect,  it  is 
only  necessary  that,  by  the  action  of  the  current,  all  the  particles 
of  hydrogen  should  be  removed  one  place  to  the  right,  or  all  the 
particles  of  oxygen  one  place  to  the  left.  That  is,  the  electrolysis 
of  every  particle  of  water  in  the  track  of  the  current  has  taken 
place,  but  the  immediate  reunion  of  all  the  particles  has  followed, 
except  the  extreme  particle  of  oxygen,  on  the  one  hand,  and  the 
extreme  hydrogen  on  the  other. 

The  oxygen  and  hydrogen  thus  liberated,  at  once  make  their 
escape;  and  the  continued  action  of  the  current  produces  a  like 
effect  on  other  particles  of  water  until  the  action  ceases,  or  all  the 
water  is  decomposed. 

115.  The  quantity  of  electricity  required  to  effect  the  decomposition 
of  any  compound  is  probably  always  the  same,  as  would  be  shown  if  we 
had  means  to  measure  it  accurately ;    and  the  relative  quantities  of 
several  electrolites  decomposed  by  a  given  quantity  of  electricity  will  be 
represented  by  the  combining  numbers  of  these  compounds.     We  shall 
hereafter  have  occasion  to  allude  to  this  point  again,  in  connection  with 
the  subject  of  combining  proportions  or  equivalents. 

116.  Electro- Metallurgy  is  the  name  applied  to  the  deposition 
of  the  metals  from  their  compounds  by  the  chemical  agency  of 
the  galvanic  current.     "We  have  seen  above  (103),  in  describing 
Daniel's  battery,  that  during  its  action  there  is  a  constant  depo- 
sition of  metallic  copper  upon  the  negative  plate.     Now,  if,  for 
the  copper  plate  in  this  arrangement,  a  medal,  or  coin,  or  other 
conducting  body  be  substituted,  the  deposition  of  the  copper  upon 
it  will  take  place  in  the  same  manner,  and  all  its  minute  pecu- 

QUESTIONS. — 115.  Is  the  quantity  of  electricity  required  to  effect  the 
came  decomposition  always  the  same  ?  116.  What  is  electro-metallurgy  t 

10 


110 


EFFECTS    OF    GALVANIC    ELECTRICITY. 


Electrotype. 


liarities  will  be  copied.     An  apparatus  of  this  kind,  called  the 
electrotype,  is  figured  below. 

A  glass  vessel  is  partly  filled  with  a  saturated 
solution  of  blue  vitriol,  and  in  this  is  placed  a 
porous  vessel,  containing  dilute  sulphuric  acid, 
and  a  rod  of  zinc,  Z,  having- a  binding  screw  at 
top.  The  medal  or  coin  to  be  copied  is  then 
suspended  in  the  vitriol  solution  by  means  of  a 
wire  inserted  in  the  binding  screw.  The  surface 
of  the  medal  on  which  the  copper  is  to  be  de- 
posited should  be  perfectly  clean,  and  the  other 
surface  should  be  protected  by  a  coating  of  wax 
or  varnish.  In  the  figure,  two  medals,  M,  M,  are 
supposed  to  be  connected  at  the  same  time  with 
the  zinc. 

A  better  method  than  the  above  is  to  use  a  regular  Smee's 
battery,  and  to  have  trie  blue  vitriol  solution  in  a  separate  ves- 
sel, as  in  the  annexed  figure. 
Then  let  the  article  to  be 
copied,  A,  be  connected  with 
the  zinc  of  the  battery,  and  a 
plate  of  copper,  C,  with  the 
silver,  both  being  suspended, 
at  a  little  distance  from  each 
other,  in  the  vitriol  solution. 
By  the  action  of  the  battery, 
the  piece  of  copper  will  be  gra- 
dually dissolved,  and  a  corresponding  deposit  of  metallic  copper 
made  upon  the  medal. 

In  the  battery  here  used,  one  of  the  zinc  plates  is  supposed  to  be 
removed,  presenting  clearly  to  view  the  plate  of  silver. 

117.  Other  metals  besides  copper  may  be  deposited  in  this  manner, 
but  a  battery  of  several  cells  is  in  most  cases  required.  The  most  im- 
portant application  that  has  been  made  of  this  discovery  is  in  depositing 
silver  ami  gold  in  thin  laminae  upon  other  metals,  called  plating  or  gild- 
ing. For  this  purpose  a  Daniel's  or  Smee's  battery  of  about  four  cells 
answers  well,  and  a  fifth,  which  is  called  the  depositing  cell.  This  is 


Electrotype. 


QUESTION. — Describe  the  apparatus  called  the  electrotype. 


ELECTRO- MAGNETISM.  Ill 

filled  with  a  solution  of  cyanide  of  potassium,  and  used  in  the  same 
manner  as  just  described  for  obtaining  a  deposit  of  copper,  except  that 
silver  or  gold  must  be  used  instead  of  the  copper,  C,  according  as  one 
or  the  other  of  these  metals  is  to  be  precipitated. 


ELECTRO-MAGNETISM. 

118.  Natural  Magnet,  or  Loadstone. — Among  the  ores  of  iron, 
pieces  are  often  found  which,  possess  the  property  of  attracting  and 
retaining  pieces  of  iron  or  steel  with  more  or  less  force,  and  are 
called  magnets  or  loadstone.     Each  magnet  always  has  two  points 
iu  which  the  attractive  force  appears  to  be  concentrated,  which 
are  called  the  poles.     They  are  always  readily  found  by  rolling 
the  magnet  in  iron  filings,  which  will  be  collected  more  at  these 
points  than  in  other  places.     Gene-         ^^^^S^^ir'^^^lfe 
rally  they  are  nearly  opposite  to  each       isS 

other.     (See  figure.)      If  a  magnet 

is  broken  into  several  pieces,  each 

always   retains   the   same    magnetic 

properties  as  the  whole  mass,  but  in  less  degree.     Sometimes  a 

magnet  has  more  than  two  poles. 

119.  If  a  magnet  be  suspended  horizontally,  by  a  thread,  or 
placed  upon  a  piece  of  cork  floating  in  a  vessel  of  water,  one  of 
the  poles  will  turn  towards  the  north,  and  is  hence  called  the 
north  pole,  and  the  other  towards  the   south,  and  is  called  the 
south  pole. 

If  two  magnets  thus  suspended  are  brought  near  each  other,  it 
will  be  found  that  like  poles  repel  each  other,  but  unlike  poles 
attract.  These  attractions  and  repulsions  extend  to  some  dis- 
tance, and  are  not  affected  by  the  interposition  of  other  bodies, 
not  capable  of  becoming  magnetic.  This  may  easily  be  shown 
by  interposing  a  pane  of  glass,  or  plate  of  copper,  or  a  thin  piece 

QUESTIONS, — 118.  What  is  the  natural  magnet,  or  loadstone?  What 
are  the  poles  ?  What  is  the  effect  if  the  magnet  be  broken  in  several 
pieces?  119.  What  is  the  north  pole?  What  the  south  pole  ?  When 
two  magnets  freely  suspended  are  brought  near  each  other,  what  is 
observed  of  like,  and  what  of  unlike  poles  ? 


112  ELECTRO-MAGNETISM. 

of  wood  between  the  two  magnets,  when  it  will  be  seen  that  the 
action  of  the  magnets  upon  each  other  is  the  same  as  before,  and 
does  not  even  suffer  diminution  by  the  interposed  substance,  except 
as  the  distance  between  them  is  increased. 

120.  Magnets  and  Diamagnets. — It  has  of  late  been  very 
satisfactorily  determined  that  all  substances  may  be  divided  into 
two  classes, — the  magnetic  and  the  diamagnetic.  To  the  first 
class  belong  all  substances  which,  like  iron,  nickel  and  cobalt, 
are  attracted  by  either  pole  of  a  magnet  when  presented  near 
them  j  and  when  shaped  into  bars  and  free"  to  move  (as  when 
suspended  by  a  thread  in  the  centre)  in  the  vicinity  of  a  magnet, 
they  arrange  themselves  in  the  direction  of  a  line  uniting  its 
IE — • —  -^ — **i  poles.  Two  bar  magnets  best  illus- 

^T         ===  "s|     trate  this  property;   when  in  the 

Masnets-  vicinity  of  each  other,  and  free  to 

move,  they  take  the  position  indicated  in  the  figure. 

The  substances  alrejady  named  are  the  only  ones  that  possess 
this  property  in  any  considerable  degree  j  but  others  have  recently 
been  added  to  the  list,  as  manganese,  chromium,  titanium,  palla- 
dium, platinum,  oxygen  gas,  &c.,  in  which  the  magnetic  property 
is  manifested  only  when  a  powerful  magnet  is  used. 

Diamagnetic  substances  are  such  as  are  .repelled  by  either  pole 
of  a  magnet,  and  when  made  into 
the  form  of  bars  and  free  to  move, 
in  the  vicinity  of  the  poles  of  a 
magnet,  arrange  themselves  at  right 
angles  to  a  line  uniting  its  poles. 
This  relative  position  of  the  magnet 
and  diamagnetic  bar  is  shown  in  the 

Magnet  and  Diarnagnet.  ° 

accompanying  ngure. 

This  diainagnetic  property  is  manifested  more  powerfully  by 
bismuth  than  by  any  other  substance,  but  phosphorus,  antimony, 
zinc,  tin,  sodium,  mercury,  copper,  gold,  glass,  ether,  alcohol,  and 
nany  other  bodies,  are  similarly  affected.  The  experiment  can 
oaly  be  shown  by  using  very  powerful  magnets. 

QUESTION. — 120.  Into  what  two  classes  may  all  substances  he  divided  ? 
How  do  magnetic  substances  arrange  themselves  when  brought  into  the 
vicinity  of  a  magnet  ?  How  do  diamagnetic  substances  ? 


ELECTRO-MAGNETISM.  US 

121.  Magnetic  Induction. — When  either  pole  of  a  magnet  is 
brought  in  contact  with  a  piece  of  soft  iron,  or  only  very  near  it, 
the  iron  itself  becomes  magnetic,  and  remains  so  until  the  magnet 
is  removed.  The  figure  following  represents  several  pieces  of 
iron,  placed  in  different  positions  near  the  poles  of  a  magnet;  on 
examination,  they  will  all  be  found  to  have  the  magnetic  property, 
their  poles  being  developed  as  indicated  by  the  letters  N  and  S. 


Magnetic  Induction. 

This  influence  of  a  magnet  upon  pieces  of  iron,  which  extends  to 
a  distance  around  its  poles,  is  called  its  inductive  influence. 

This  influence  is  exerted  by  a  powerful  magnet  to  a 
considerable  distance  from  either  pole,  or  even  through 
other  bodies  (119)  which  are  not  themselves  capable  of 
becoming  magnetic. 

A  piece  of  iron  or  other  substance  which  is  attracted 
by  either  pole  of  a  magnet,  is  evidently  first  rendered 
magnetic  by  induction,  and  then  the  attraction  follows  as 
a  necessary  consequence.  But  the  first  piece,  as  a  nail, 
being  rendered  magnetic  by  induction,  will  act  in  like 
manner  upon  a  second,  and  this  upon  a  third,  and  so  on; 
so  that  several  pieces  may  be  lifted  one  after  another,  as 
represented  in  the  figure.  But  it  will  be  found,  when 
the  connection  with  the  first  magnet  is  broken,  the  pieces 
of  iron  instantly  lose  their  magnetism,  and  fall  asunder. 

122.  Pieces  of  hardened  steel  will  also  be  affected  in 
a  similar  manner,  but  much  less  readily,  and,  unlike 

QUESTIONS.  — 121.  What  is  the  effect  when  either  pole  of  a  magnet  is 
brought  near  "a  piece  of  soft  iron  ?     What  is  meant  by  magnetic  induc- 
tion ?     Why  is  a  piece  of  soft  iron  attracted  by  a  magnet  ? 
10* 


114  ELECTED- MAGNETISM. 

iron,  they  retain  the  magnetism  that  has  been  induced.  They 
therefore  become  permanently  magnetic,  and  for  nearly  every 
purpose  are  superior  to  the  natural  magnet,  and  may  be  denomi- 
nated artificial  magnets.  The 'same  magnet  may  be  used  suc- 
cessively to  magnetize  any  number  of  steel  bars,  without  losing 
any  of  its  virtue;  from  which  it  follows  that  the  magnet  commu- 
nicates nothing  to  them,  but  only  by  its  influence  developes  some 
hidden  principle  already  there.  Artificial  magnets  are  frequently 
made  in  the  form  of  the  horse-shoe,  and  are  called  horse-shoe 
magnets.  To  the  poles  a  short  piece  of  soft  iron  is  usually 
accurately  fitted,  called  the  armature  or  keeper. 

123.  The  Magnetic  Needle— Dipping  Needle.— A  slender  bar 
of  magnetized   steel,  suspended  upon   a   pivot,  so  as  to  revolve 
freely,  constitutes  the  magnetic  needle.     Sometimes  it  is  attached 
to  a  circular  card,  and  suspended  upon  a  pivot,  as  in  the  mariner's 
compass. 

124.  If  a  steel  bar  be  suspended  by  its  centre  of  gravity,  and 
afterwards  carefully  magnetized,  it  will  be  found  not  only  to  place 
itself  in  the  magnetic  meridian,  but  to  assume  a  position  inclined 
to  the  horizon.     In  northern  latitudes,  the  north  pole  will  be 
depressed  and  the  south  pole  elevated,  while  in  southern  latitudes 
the  south  pole  will  be  depressed.     The  angle  of  inclination  is 
generally  nearly  the  same  in  the  same  place,  and  is  called  the 
dip  of  the  needle;   and  a  needle  nicely  balanced  and  adjusted  for 
showing  the  dip  is  called  a  dipping  needle. 

The  dip  of  the  needle  is  subject  to  considerable  variation,  but  at  the 
present  time  it  is,  at  Baltimore,  about  71°  30';  at  Philadelphia,  72°  15'; 
at  New  York,  73°  ;  at  Middletown,  Conn.,  73°  30' ;  and  at  Boston,  74°  24. 

The  magnetic  needle  does  not  always  point  to  the  true  north  and  south, 
but  deviates  more  or  less  from  this  position  at  different  times  and  places. 
This  is  called  its  variation.  At  Philadelphia,  in  1840,  the  variation  was 
8°  52'  W.,  and  at  Middletown,  Conn.,  about  6°  40'. 

125.  Terrestrial  Magnetism.— The  earth  may  be  considered 
as  a  great  natural  magnet,  which,  by  its  action  on  the  needle,  in 
the  same  manner  as  any  .other  magnet,  causes  it  to  place  itself  in 

QUESTIONS. — 122.  May  magnetism  be  induced  in  pieces  of  tempered 
steel?  What  are  artificial  magnets ?  123.  What  constitutes  the  magnetic 
needle?  124.  What  is  a  dipping  needle?  125.  What  may  the  earth  be 
considered  ? 


ELECTRO-MAGNETISM.  115 

the  position  of  north  and  south.  Indeed,  it  is  by  the  inductive 
influence  of  the  earth  that  magnetism  is  developed  in  bodies  upon 
its  surface.  This  is  shown  in  bars  of  iron  or  steel  that  have  stood 
long  in  a  vertical  position,  which  are  always  found  to  be  magnetic. 
Tongs  and  pokers,  from  their  being  usually  kept  in  an  upright 
position,  are  almost  always  found  to  be  magnetic. 

As  it  has  been  agreed  to  call  that  pole  of  the  needle  which 
points  northward,  the  north  pole,  it  is  evident  that'  the  pole  of 
the  earth  situated  'north  must  be  a  south  pole;  that  is,  it  must 
possess  southern  polarity.  So,  also,  the  south  pole  of  the  earth 
must  possess  northern  polarity. 

126.  Relation  between  the  Electric  Current  and  Magnetism. 
— It  has  been  long  known  that  a  discharge  of  lightning  will  often 
affect  seriously  the  magnetic  needle,  sometimes  reversing  its  poles  j 
but  it  was  not  until  1819  that  (Ersted  made  his  famous  discovery, 
which  has  served  as  the  basis  of  the  beautiful  science  of  Electro- 
Magnetism. 

He  first  observed  that  when  the  wire,  connecting  the  electrodes 
of  an  active  galvanic  battery,  is  brought  near  a  magnetic  needle, 
it  is  made  to  deviate  from  its  ordinary  position,  and  assume  a  new 
one,  depending  upon  the  direction  of  the  current  and  the  position 
of  the  wire  in  regard  to  the  needle.  Thus,  the  needle  being  in 
its  natural  position, — 1st,  if  the  connecting  wire  be  above  the 
needle  and  parallel  to  it,  the  pole  next  the  negative  electrode  will 
move  westward;  2d,  if  the  wire  be  ?£*>  = 

beneath  the  needle,  it  will  move  east-  "  fl J 

ward ;  3d,  if  the  wire  is  on  the  west  \ 
side,  this  pole  will  be  depressed ;  and, 
4th,  if  ifc.  be  on  the  east  side,  it  will 
be  elevated.  The  figure  in  the  margin 
indicates  the  motion  that  will  be  pro- 
duced in  the  first  of  the  above  cases.  Cnm-nt  uua  Needle. 

If  the  wire  be  placed  under  the  needle,  and  the  current  made 


QUESTIONS. — Why  do  tongs  and  pokers  become  magnetic  by  standing 
in  a  vertical  position?  What  is  said  of  the  north  >md  south  poles  of  the 
earth?  126.  What  was  the  fact  first  observed  by  (Ersted  as  regards  the 
•wire  conducting  a  galvanic  current  and  a  magnet? 


116 


ELECTHO-  MAGNETISM. 


Current  and  Needle. 


to  pass  from  north  to  south,  the  motion  of  the  needle  will  be  the 
game  as  indicated  in  the  figure. 

It  follows,  therefore,  if  the  wire  be  bent  around  the  needle,  in 
the  form  of  a  rectangle,  so  as  to 
~  convey  the  current  in  one  direction 
J  above  the  needle,  and  back  again,  in 
the  opposite  direction  beneath  it, 
both  parts  will  conspire  to  produce 
the  same  effect,  and  the  motion  of 
the  needle  will  be  much  increased. 
Such  an  arrangement  is  represented 
in  the  annexed  figure. 
In  all  these  cases,  the  tendency  of  the  needle  is  to  settle 
directly  across  the  wire,  or  at  right  angles  to  the  direction  of 
the  current,  while  the  influence  of  the  earth  is  exerted  to  bring 
it  in  its  first  position,  parallel  with  the  wire,  supposing  the  experi- 
ment to  be  commenced  with  the  needle  in  its  natural  position. 
The  position  it  will  ultimately  take  will  therefore  be  intermediate 
between  these  two. 

127.  To  avoid  the  directive  influence  of  the  earth  upon  the 
needle,  the  astatic  (from  the  Greek  astatos,  unstable)  needle  has 
been  contrived.  It  consists  of  two  needles,  of  nearly  equal 
strength,  fixed  to  the  same  axis,  with  their 
poles  reversed  in  reference  to  each  other,  and 
suspended  by  a  thread,  as  shown  in  the 
figure.  One  of  the  needles  being  a  little 
more  highly  magnetized  than  the  other,  or 
a  little  larger,  they  will  have  a  slight  ten- 
dency to  settle  in  the  meridian.  If,  now,  a 
wire  is  bent  several  times  around  the  lower 
needle,  each  turn  or  coil  being  coated  with  some  insulating  sub- 
stance, when  the  current  is  passed  around  it,  its  influence  on 
both  needles  will  be  to  turn  them  in  the  same  direction;  and  the 


Astatic  Needle. 


QUESTIONS. — What  is  the  effect  if  the  wire  is  bent  around  so  as  to 
pass  several  times  around  the  needle?  What  is  the  real  tendency 
of  the  needle?  127.  What  is  the  astatic  needle?  Describe  its  con- 
etruction. 


ELECTRO-MAGNETISM. 


117 


Astatic  Needle. 


arrangement  becomes  a  most  delicate  in- 
strument for 'indicating  the  passage  of 
the  feeblest  currents.  Such  an  instru- 
ment is  called  a  galvanometer,  or  gal- 
vanoscope.  To  protect  it  from  currents 
of  air,  the  whole  is  usually  enclosed  in 
a  glass  case;  and  beneath  the  upper 
needle,  and  above  the  coil  of  wire,  a 
graduated  circle  is  placed,  to  indicate 
exactly  the  comparative  deflections  of  the 
needle. 

Such  an  instrument,  in  connection 
with  a  thermo-electric  pile  (93),  becomes 
a  most  delicate  thermometer,  which  is 
capable  of  indicating  a  change  of  tem- 
perature of  only  a  very  small  fraction  of 
a  degree. 

128,  Tangential  Force, — By  a  careful  inspection  of  the  motions 
produced  in  the  needle  by  the  current  in  the  several  positions  of 
the  wire,  as  described  in  paragraph  126,  it  will  be  evident  that 
the  real  tendency  of  each  pole  is  to  revolve  around  the  connecting 
wire  in  a  cir'cle,  the  plane  of  which  is  perpendicular  to  the  wire; — 
around  the  north  pole  in  one  direction  and  around  the  south  pole 
in  the  other.  The  force  which  causes  tffis  motion  is  exerted  in 
lines  which  are  tangents  to  the  circumference  of  these  circles,  and 
is  therefore  called  a  tangential  force. 

The  motion  of  the  needle  actually  produced  will  of  course 
depend  upon  the  mode  in  which  it  is  supported,  as  well  as  the 
position  of  the  wire  in  reference  to  it.  It  is  to  be  remarked,  too, 
that  the  pole  is  a  mere  point  situated  near  the  extremity  of  the 
needle ; — between  this  point  and  the  wire  the  force  is  exerted. 
This  point, — the  magnetic  pole — cannot  exist  independent  of 
the  needle  itself,  which  must  ther  fore  always  move  with  it;  and 
therefore  in  order  to  determine  the  real  motion  in  any  particular* 

QUESTIONS. — Describe  the  galvanometer,  or  galvanoscope.  128.  What 
is  the  real  tendency  of  each  pole  of  a  magnet  when  brought  near  the 
wire?  What  is  the  force  called  which  produces  this  motion?  Upon 
•what  will  the  motion  actually  produced  depend  ? 


118 


ELECTRO-MAGNETISM. 


N 

Pole  Revolves. 


case  we  are  to  consider  the  two  circumstances, — First,  the  motion 
the  pole  tends  to  make,  and  Secondly,  the  motion*of  which  the 
needle  is  susceptible.  Upon  these  two  conditions  plainly  will 
depend  the  actual  motion  that  will  result. 

129.  In  order  easily  to  remember  the  particular  motion  a  pole 
will  tend  to  make  in  any  given  case,  take  the  following  example. 
Let  us  suppose  the  conducting  wire  to  be  placed  in  a  vertical 

position,  and  the  current  of  posi- 
tive electricity  to  be  descending 
through  it,  the  tendency  of  a  north 
pole  in  the  vicinity  of  the  wire 
will  be  to  move  around  it  in  a  hori- 
zontal circle,  in  the  direction  indi- 
cated by  the  arrows  in  the  figure, 
or  in  the  direction  of  the  hands 
of  a  watch  with  the  dial  upward. 
The  tendency  of  the  south  pole 
would  be  to  revolve  in  the  opposite  direction.  If  the  direction 
of  the  electrical  current  is  reversed,  and  it  is  made  to  pass  up- 
ward, both  poles  would  tend  to  revolve  in  the  opposite  direction 
from  that  described  above.  Whatever  may  be  the  position  of 
Jthe  conducting  wire  with  reference  to  the  needle,  the  motions 
produced  will  always  be  in  accordance  with  these  statements;  and 
reference  being  had  to  this  particular  position  of  the  conducting 
wire  and  the  needle,  we  can  always  determine  by  inspection  in 
what  direction  the  needle  will  move,  whatever  may  be  the  position 
of  the  wire  in  regard  to  it. 

We  have  here  been  speaking  only  of  motions  produced  in  the 
needle  by  the  conducting  wire;  but  it  is  plain  that  if  the  pole  of 
a  magnetic  needle  tends  to  revolve  around  a  fixed  conducting 
wire,  a  free  wire  will  have  a  tendency  to  revolve  around  the  pole 
of  a  fixed  needle.  The  fact  is,  Jhe  influence  is  mutual,  and  both 
fie  wire  and  the  pole  tend  to  i Evolve,  as  we  will  proceed  to  show. 

QUESTIONS. — To  determine  the  real  motion  that  will  be  produced  in  a 
given  case,  what  two  things  are  to  be  considered  ?  129.  When  the  cur- 
rent is  descending  perpendicularly,  what  will  be  the  tendency  of  the 
north  pole  of  a  needle  in  the  vicinity  of  the  wire  ? 


ELECTRO-MAGNETISM. 


119 


130.  Both  the  revolution  of  a  pole  around  a  fixed  wire,  and  the 
revolution  of  a  wire  around  a  fixed  pole,  may  be  shown  by  the 
apparatus,  a  section  of 

which  is  seen  in  the  cut 
in  the  margin.  A  and 
B  are  two  glass  vessels, 
filled  nearly  to  the  top 
with  mercury.  A  wire, 
supported  by  a  pillar  be- 
tween the  vessels,  has 
one  end  bent  down  so 
as  to  dip  into  the  mer- 
cury in  A;  and  the  other 
end  is  bent  into  a  hook, 

,  .    ,  ,  •  •       Both  Pole  and  Connecting  Wire  revolve. 

on  which  a  short   piece 

of  wire  is  suspended,  so  that  its  lower  end  shall  also  dip  into  the 
mercury  in  the  vessel  B.  Conducting  wires  pass  through  the 
bottoms  of  both  vessels,  with  binding  screws,  C  and  D,  to  connect 
them  with  the  poles  of  the  battery;  and  to  that  in  A,  a  small 
magnet  is  attached  by  a  thread,  so  that  one  of  its  poles  may  be  a 
little  above  the  surface  of  the  mercury;  and  in  the  vessel  B 
another  small  magnet  is. firmly  fixed,  with  one  pole  a  little  above 
the  mercury.  When  the  current  is  passed  through  this  apparatus, 
as  indicated  by  the  arrows,  the  upper  pole  of  the  magnet  in  A 
will  revolve  slowly  around  the  conducting  wire,  and  the  free  con- 
ducting wire  suspended  in  B  will  revolve  around  the  fixed  pole 
near  it. 

131.  Further  Experiments  illustrating  the  Relation  of  the 
Magnet  and  a  Galvanic  Current. — Experiments  to  illustrate  the 
relation  of  a  current  and  the  magnet  may  be  multiplied  almost 
indefinitely! 

De  la  Rive's  Ring  is  a  very  beautiful  contrivance  to  show  the 
influence  of  a  magnetic  pole  upon  a  conducting  wire  capable  of 
motion.  A  copper  wire  is  bent  into  a  circle  about  an  inch  in 


QUESTIONS. — 130.  Describe  the  apparatus  figured  in  paragraph  130. 
What  is  the  point  illustrated  ? 


120  ELECTRO- MAGNETISM. 

diameter,  and  the  two  ends-  passed  through  a  piece  of  wood  or 
~  cork,  and  soldered,  one  to  a  slip  of 

zinc,  Z,  and  the  other  to  a  slip  of 
copper,  C.  If,  now,  it  be  placed  in 
a  bowl  of  water  containing  a  little 
acid,  a  current  of  electricity  will  cir- 
culate along  the  wire,  in  the  direction 
of  the  arrows ;  and  if  a  bar  magnet 

De  la  Rive's  Ring.  be  brought  near  it>  Jt  W;U  be  attracted 

or  repelled,  according  as  one  pole  or  the  other  of  the  magnet  is 
presented  to  it.  As  represented  in  the  figure,  if  the  north  pole 
of  the  magnet  is  -presented  to  it,  it  will  be  attracted ;  the  south 
pole  will  first  repel  it,  but  in  a  little  time  it  will  turn  around,  and 
will  then  be  attracted.  We  may,  therefore,  properly  regard  it  as 
a  flat  magnet,  having  its  two  poles  in  the  centre  of  the  circle,  the 
one  on  one  side,  and  the  other  on  the  other ;  the  south  pole  being 
in  that  surface  on  which,  when  held  before  you,  the  positive  cur- 
rent flows  in  the  direction  of  the  hands  of  a  watch.  The  apparatus 
will  be  more  powerful  if  the  conducting  wire,  covered  with  silk, 
to  prevent  lateral  communication,  be  formed  into  several  circles 
of  the  same  diameter,  on  the  principle  of  the  multiplier. 

132.  But  what  are  the  forces  that  have  produced  these  special 
movements?  Giving  our  attention  for  the  present  only  to  the 
part  of  the  current  upward  on  one  side  of  the  ring  and  downward 
on  the  other,  we  have  seen  (129)  that  the  downward  current  tends 
to  revolve  around  the  north  pole  of  a  needle  in  the  direction  of 
the  hands  of  a  watch,  and  the  upward  current  in  the  opposite 
direction ;  let  these  facts  be  kept  in  mind  while  the  eye  rests  upon 
the  figure,  and  it  is  plain  that  the  effect  must  be  to  cause  the  ring 
to  approach  the  pole,  or  apparent  attraction  ensues.  If,  now,  the 
magnet  be  suddenly  removed,  and  the  south  pole  presented,  in 
accordance  with  the  .same  laws,  the  ring  recedes,  turns  around, 
..  nd  again  approaches  the  pole  ! 

QUESTIONS. — 131.    Describe   De  la  Rive's  Ring,   and   the  mode   o 
using  it.     What  may  we  regard  it  ?     132.  Give  the  reasons  for  theso 
movements. 


ELECTRO- MAGNETISM. 


121 


133.  The  galvanoscope  is  represented  by  the  next  figure 
N  and  S  are  the  north  and  south  poles  of  a 
permanent  horse-shoe  magnet,  supported  upon 
a  stand;  and  between  them,  in  a  small  glass 
tube,  is  a  strip  of  gold  leaf,  connected  at  top 
and  bottom  with  binding  screws,  as  shown  in 
the  figure.  Now  when  the  current  is  passed 
through  the  gold  leaf,  it  is  made  to  curve  to  one 
side  or  the  other,  according  as  the  motion  of  the 
current  is  upward  or  downward.  As  the  poles 
are  situated  in  the  figure,  if  the  direction  of  the 
current  is  downward,  the  curving  or  convexity 
of  the  gold  leaf  will  be  upward  froni  the  plane 
of  the  paper  j  but  if  the  current  is  upward  the 
strip  of  gold  leaf  will  be  convex  in  the  opposite 
direction,  or  backward  from  the  plane  of  the 


134,  The  Revolving  Spur  Wheel,  figured  in  the  margin,  is 
made  to  revolve  by  the 
action  of  a  magnet  upon 
the  galvanic  current.  A 
wheel  W  mad,e  of  sheet 
brass,  is  supported  in 
such  a  manner  that  its 
rays  touch  in  a  globule 
of  mercury  in  the  base 
beneath,  from  which  a 
concealed  wire  extends 
to  the  binding  screw  A, 
the  other  binding  screw 
B  being  connected,  in 

like    manner,   with    the  Revolving  wheel, 

wire  R  which  supports  the  wheel.     N  S  is  a  magnet  placed  so 

QUESTIONS. — 13£.  Describe  the  galvanoscope.      134.   Describe  the  re- 
volving spur  wheel  *  and  give  the  reasons  for  the  movement  produced. 
11 


122 


ELECTRO-MAGNETISM, 


that  its  poles  shall  be  as  nearly  as  possible  one  on  each  side  of 
the  ray  of  the  wheel  which  for  the  time  is  in  contact  with  the 
mercury.  When  the  poles  of  the  galvanic  battery  are  connected 
with  the  binding  screws,  a  ray  of  the  wheel  being  in  contact  with 
the  globule  of  mercury,  the  current  passes  through  it;  and  £he 
wheel  is  made  to  revolve  on  its  axis.  A  permanent  magnet  may 
be  used,  or  an  electro-magnet,  as  represented  in  the  figure  (p.  121). 

135,  Relation  of  Current  to  the  Earth's  Magnetism,— The 
ring  described  in  paragraph  131  is  acted  upon  by  the  earth's 
magnetism  precisely  in  the  same  manner  as  by  the  magnet,  only 
that  the  influence  is  less  in  degree.  In  order  that  it  may  be  made 
to  move  by  the  magnetism  of  the  earth,  it  is  only  necessary  that 
it  should  be  enlarged  sufficiently,  and  a  powerful  current  passed 
through  it.  The  following  modification  of  it  answers  a  good 
purpose. 

Let  A  and  B  be  two 
metallic  pillars,  insulated 
from  each  other,  provided 
each  with  a  horizontal  arm 
terminating  in  a  small  cup 
filled  with  mercury,  and 
connected  at  the  bottom 
with  binding  screws.  Let 
a  ring  R  of  copper  wire, 
8  or  10  inches  in  diameter, 
be  suspended  by  the  ends 
of  the  wire  from  the  cups 
of  mercury,  and  the  poles 
of  the  battery  connected 
with  the  binding  screws ; — the  current  will  pass  around  the  circle 
of  wire,  which,  by  the  influence  of  the  earth's  magnetism,  will  be 
made  to  move  until  at  length  it  will  take  a  position  with  its  plane 
at  right  angles  to  the  meridian.  Supposing  the  direction  of  the 
current  to  be  as  indicated  by  the  arrows,  and  recollecting  that  the 

QUESTIONS. — 135.  Does  the  earth's  magnetism  act  upon  a  current  in 
the  same  manner  as  a  magnet?  Describe  the  movegneuts  produced  in 
the  ring  here  figured  when  conveying  the  current  by  virtue  of  the 
earth's  magnetism. 


Influence  of  Earth. 


ELECTRO-MAGNETISM.  128 

north. pole  of  the  earth  really  possesses  southern  (125)  polarity, 
let  the  intelligent  student  determine  which  side  of  the  circle  of 
wire  will  settle  to  the  east  and  which  to  the  west ! 

It  may  afford  some  aid  to  reflect  that  the  action  on  the  circle 
of  wire  will  be  the  same  as  if  it  were  square, 
as  shown  in  the  margin,  in  which  it  appears 
there  are  four  parts  conveying  the  current, 
two  on  which  its  motion  is  horizontal  in  oppo- 
site directions  and  on  the  same  side  of  the 
point  of  support.  The  influence  of  these  is 
lost  and  may  not  therefore  be  further  con- 
sidered. On  the  other  two  parts  the  motion 
of  the  current  is  in  opposite  directions, — 


being  on  one  upward  and  on  the  other  down-  upward  and  Downward 
ward — and  on  opposite  sides  of  the  point  of 
support.  Now  the  tendency  of  the  part  conveying  the  upward 
current  will  be  to  revolve  round  the  north  pole  of  the  earth  in 
one  direction,  and  of  the  part  conveying  the  downward  current  to 
revolve  around  this  pole  in  the  opposite  direction;  considering 
then  the  mode  in  which  the  wire  is  suspended,  it  is  plain  that  the 
tendency  of  the  circle  of  wire  will  be  to  settle  with  its  plane  due 
east  and  west,  or  at  right  angles  to  the  meridian.  If,  then,  before 
passing  the  current,  the  plane  of  the  circle  of  wire  is  placed  in  the 
meridian  when  the  current  is  made  to  pass  it  will  turn  on  its 
points  of  support  until  it  takes  a  position  at  right  angles  to  the 
meridian.  In  every  case,  the  side  of  the  circle  conveying  the 
downward  current  will  move  towards  the  east,  and  the  other  side 
of  course  towards  the  west. 

The  same  movement  will  be  produced  if  the  wire  conveying  the 
current  is  bent  several  times  around,  as  represented  in  the  first  figure 
on  the  next  page,  and  supported  by  its  two  ends  resting  in  cups 
of  mercury,  with  which  the  two  poles  of  the  battery  are  to  be 
connected  by  binding  screws  not  represented  in  the  figure.  The 
influence  of  each  coil  conspires  to  produce  the  same  effect,  and 
therefore  the  motions  described  will  foe  more  readily  produced. 

QUESTIONS. — Explain  the  reasons  for  the  motions  which  are  produced 
by  the  earth's  magnetism,  as  illustrated  by  the  preceding  figure,  and  also 
the  two  figures  on  the  next  page. 


124 


ELECTRO- MAGNET ISM. 


But  it  is  not  necessary  that  the  dif- 
ferent coils  of  the  wire  should  lie  in  the 
same  plane,  the  result  being  the  same 
if  it  is  wound  in  the  form  of  a  helix, 


Influence  of  Earth's  Magnetism. 

as  represented  in  the  next  figure;   the  helix  then  truly  repre- 
senting a  bar  magnet,  as  will  be  found  by  holding  either  pole  of  a 
magnet  near  either  end. 

By  examining  the  direction  of  the  current  in  this  helix,  con- 
sidering it  as  a  bar  magnet,  it  will  be  found  that  is  the  south  pole 
in  which  (when  it  is  held  up  before  the  eye)  the  current  is  moving 
in  the  direction  of  the  hands  of  a  watch.     It  is  scarcely  necessary 
to  remark  that,  in  the  other  pole,  the  direction  of  the  current  is 
the  reverse  of  this. 

136.  Induction  of  Magnetism  by  a  Current. — Magnetism  is 
induced  in  a  bar  of  soft  iron  by  the  simple 
passage  of  a  current  near  it,  in  a  direction  at 
right  angles  to  the  bar.     Thus,  if  W I  be  the 
=======  conducting  wire,  and  N  S  a  small  piece  of  iron 

lying  under  the  wire,  while  the  current  is  pass- 
ing, magnetic  polarity  will  be  induced  in  the 
induction  of  Magnetism -iron,  N  being  a  north  pole,  and  S  a  south 

by  a  Current.  p0]e?  w^en   the    current   passes   frpm  W  »tO   I; 

but  if  the  current  pass  from  I  to  W,  the  poles  will  be  reversed.       f 
But,  if  the  wire  is  made  to  pass  around  the  iron  many  times,  • 
the  effect  will  be  greatly  increased.      This  is  accomplished   by 

QUESTIONS. — When  the  south  pole  of  the  helix  is  held  up  before  the* 
face,  in  what  direction  is  the  current  found  to  be  moving  ?     136.  How 
is  magnetism  induced  in  a  piece  of  iron  by  the  galvanic  current? 


ELECTRO- MAGNETISM 


125 


placing  the  iron  in  a  helix  of  wire,  as  shown  in  the  figure.     The 

current  being  then  made  to    p 

pass  in  the  direction  of  the 

arrows,    the     iron    becomes 

strongly   magnetic,   with   its 

poles  as  shown  by  the  letters 

N  and  S.     The  cups  P  and 

__  *   .,        ...  induction  of  Magnetism  by  a  Current. 

N  serve  to  connect  it  with  , 

the  battery.  When  the  current  is  broken,  the  iron  ceases  at  once 
to  be  magnetic ;  but  if  a  piece  of  hardened  steel  be  substituted 
for  the  iron,  it  retains  its  magnetism  permanently. 

A  magnet  formed  in  this  manner,  by  the  passage  of  a  current 
of  electricity  around  it,  is  very  properly  termed  an 
electro-magnet.  Magnets  of  this  kind  have  some- 
times been  made  of  sufficient  strength  to  sustain  a 
weight  of  2000  or  even  3000  pounds.  For  this  pur- 
pose, a  bar  of  iron  of  considerable  size  is  bent  in  the 
form  of  a  horse- shoe,  and  the  conducting  wire  made 
to  pass  many  times  around  it,  as  represented  in  the 
figure.  An  armature  of  soft  iron  (122)  is  attached 
to  the  poles,  as  with  the  common  magnet,  from  which 
the  weights  are  suspended.  As  stated  above,  when  the  current  of 
electricity  is  interrupted,  the  magnetism  will  be  im- 
mediately destroyed,  and  the  weights  drop  off. 

137.  The  Magic  Circle,  as  it  has  been  termed, 
possesses  too  much  interest  to  be  here  omitted, 
though  no  new  principle  is  developed  by  its  action. 
Two  semi-ci*cles,  A  and  B,  are  made  of  a  stout  bar 
of  soft  iron,  and  well  fitted  together,  so  as  to  form 
a  circle,  C,  and  include  a  small  helix  of  wire,  H, 
the  two  ends  of  which  are  to  be  connected  with  the 
electrodes  of  a  small  but  active  battery.  While  the 
current  is  passing,  the  semi-circles  are  made  power- 
folly  magnetic,  and  will  adhere  with  a  force  which 
is  capable  of  sustaining  a  weight  of  many  pounds.  Ma^-ic  Circle. 

QUESTIONS. — What  is  the  effect  when  the  current  is  made  to  pass  many- 
times  around  the  piece  of  iron  ?     What  constitutes  the  electro-magnet  t 
137.  Describe  the  magic  circle. 
11* 


126  ELECTRO- MAGNETISM. 

The  wire  need  in  all  these  arrangements  is  supposed  to  be  wound 
with  some  insulating  substance,  as  silk  or  cotton,  to  prevent  the 
contact  of  the  separate  coils,  which  would  permit  a  lateral  discharge 
of  the  current,  so  that  it  would  not  pass  around  the  whole  length 
of  the  wire. 

138.  To  form  an  effective  electro-magnet,  the  total  length  of 
copper  wire  intended  to  be  used  is  cut  into  several  portions,  each 
of  which,  covered  with  thread,  is  coiled  separately  on  the  iron. 
The  ends  of  all  the  wires  are  then  collected  into  separate  parcels, 
and  are  made  to  communicate  with  the  same  battery,  taking  care 
that  the  positive  current  shall  pass  along  each  wire  in  the  same 
direction.     The  current  is  thus  divided  into  a  number  of  branches, 
and  has  only  a  short  passage  from  one  end  of  the  battery  to  the 
other,  though  it  gives  energy  to  a  multitude  of  coils.     This  was 
first  made  known  by  Prof.  Henry,  now  Secretary  of  the  Smith- 
sonian Institution. 

139.  Magnetism  of  the  Earth. — We  have  seen  above  (125) 
that  the  earth  may  be  considered  as  a  great  magnet,  having  its 
south  pole  somewhere  near  its  north  geographical  pole,  and  its 
north  pole  near  its  south  geographical  pole;  and  it  has  been  sug- 
gested that  this  may  be  occasioned  by  currents  of  electricity  flow- 
ing around  it,  beneath  its  surface,  from  east  to  west,  or  in  the 
direction  opposite  to  that  of  its  motion  on  its  axis.     Indeed,  it  has 
even  been  suggested  that  these  currents  may  have  their  origin  in 
the  heating  influence  of  the  sun's  rays,  as  successive  portions  of 
the  earth's  surface  come  under  their  influence  by  its  daily  motion ; 

but  this  is  to  be  regarded  as  only  plausible 
conjecture.  That  the  needle  would  be  in- 
fluenced by  such  a  current,  precisely  as  it 
really  is,  at  different  points  of  the  earth's 
surface,  may  be  shown  by  winding  a 
covered  wire  several  times  around  the 
equator  of  a  common  globe,  and  placing 
a  small  magnetic  needle  upon  it  while 
the  current  is  passing,  as  shown  in  the 

QUESTIONS. — Why  must  the  wire  used  for  this  purpose  be  wound  wither 
some  non-conducting  substance?     ]88.  What  is  said  of  the  total  length 
of  wire  used  for  this  purpose?     139.  What  is  said  of  the  earth  in  refer- 
ence to  this  subject?     How  may  the  magnetism  of  the  earth  be  occa- 
sioned ?     Describe  the  figure  in  this  paragraph. 


1;  L  E  C  K  R  *>  -  MAGNETISM. 


127 


figure  (p.  126).     The  small  needle  will  uniformly  settle  in  the 
meridian. 

140,  Electro-magnetic  Engines, — All  the  above  motions,  it 
will  be  observed,  whether  of  the  magnetic  needle  or  of  the  con- 
ducting wire,  have  been  produced  by  the  tangential  force;  but 
various  machines  have  been  devised,  called  electro-magnetic  engines, 
for  producing  motion  by  direct  influence  upon  each  other  of  th.. 
unlike  and  like  poles  of  two  or  more  magnets ;  "one  of  which  a< 
least  must  be  an  electro-magnet. 

The  next  figure  represents  a  very  simple  electro-magnetic  machine, 
•which  by  its  motion  rings  a  bell  with  considerable  force.  N  and  S  £6re  the 
north  and  south  poles  of  a  common  horse- 
shoe magnet,  which  stands  in  a  vertical 
position,  with  its  poles  downward.  A  is 
a  piece  of  soft  iron  wound  with  copper 
wire  and  fixed  upon  a  vertical  axis,  so  as 
to  revolve  very  accurately  between  the 
poles  of  a  magnet;  and  CC  are  binding 
screws  for  connecting  the  wires  from  the 
galvanic  battery.  The  extremities  of  the 
wire  around  the  magnet  A  connect  with 
0  C,  by  means  of  parts  not  represented  in 
the  figure,  in  such  a  manner  that  the 
current  flows  in  the  proper  direction  to 
develope  north  polarity  in  the  further  ex- 
tremity A  as  it  approaches  the  south  pole 
of  the  magnet  S,  and  south  polarity  in  the 
other  extremity  as  it  approaches  the  north 
pole  N  :  but  the  momeiit  the  revolving 
magnet  has  arrived  at  a  position  between 
N  aiid  S,  the  two  poles  of  the  stationary 
magnet,  where  it  would  be  held  if  the 
Bame  polarity  remained,  the  direction  of 
the  current  is  reversed,  and,  as  a  neces- 
sary consequence,  the  polarity  of  the  re- 
volving magnet.  If  its  momentum  has 
now  carried  it  a  little  beyond  the  point, 
of  greatest  attraction,  it  will  be  urged 
on  by  repulsion  until  it  has  made  a 
quarter  of  a  revolution,  when  it  will  be 
attracted  as  before.  At  S  on  the  vert:c;il 
axis  is  a  perpetual  Screw  which  acts  upon 
the  teeth  of  a  ratchet  wheel,  and  causes  the  hammer  to  strike  the  bell  B 

The  machine  may  be  constructed  with  more  than  two  magnets,  and  i.1 
a  variety  of  forms,  but  whether  it  will  ever  be  made  practically  useful 
-,  remains  to' be  'determined. 


Electro-magnetic  Engine. 


QUESTIONS.  — 140.  What  are  electro -magnetic    nginesf      Describe   thf 
engine  represented  in  the  figure. 


128 


ELECTRO- MAGNET ISM. 


141.  Mutual  Influence  of  Two  Currents.— Two  currents  moving 
in  the  same  direction  in  the  vicinity  of  each  other  are  mutually 
attracted,  but  if  moving  in  opposite  directions  they  repel  each 
other. 

Let  a  helix  of  slender  wire  be  sus- 
pended by  the  top  so  that  the  bot- 
tom   may  just  touch  in   a  cup  of 
mercury;   and  let  a  current  from  a 
battery  be   passed  through  it.     In 
consequence    of  the  attractions  be- 
tween  the  coils,  the  spiral  will  be 
shortened,  and  the  lower  end  raised 
from  the  mercury,  thus  breaking  the 
circuit.    But  when  the  current  ceases 
the  end  of  the  wire  again  falls  so  as 
to  touch  the  mercury,  and  the  cur- 
Attraction.  rent  -ls  renewe(j  wifch  the  same  effects 
as  before.     Every  time  the  wire  touches  the  mercury  a  brilliant 
spark  is  produced.     Two  currents  therefore  in  the  same  direction 
attract  each  other. 

142, "  Electro-Dynamic  Induction. — A  current  of  electricity 
passing  through  a  conductor  in  a  given  direction,  induces  a  cur- 
rent in   the   opposite  direction    in   a  second  conductor  situated 
parallel  to  the  first.     Thus,  let  A  B  be  a  portion  of  a  wire  con- 
+  A  B        necting  the  poles  of  a  gal- 

===a==========^^  vanic   battery,  and  MN  a 

-  +     portion    of    a   second   wire 

M  N      parallel,    and    near   to    the 

first;— at  the   moment  the 

circuit  is  formed  and  the  current  passes  through  the  first  wire  in 
the  direction  from  -f  to  —  a  secondary  current  is  induced  in  the 
second  wire  in  the  opposite  direction.  This  current  is  but  for  an 
instant,  but  is  renewed  in  the  opposite  direction  when  the  battery 
current  is  again  broken. 

QUESTIONS. — 141.  How  do  two  currents  moving  in  the  same  direction 
affect  each  other?  Describe  the  experiment  illustrated  in  the  annexed 
figure.  142.  How  may  a  current  be  made  to  induce  another  current 
called  a  secondary  current  ? 


ELECTRO- MAGNETISM.  129 

A  better  method  to  demonstrate  the  existence  of  this  secondary 
current  is  as  follows :  Let  A  be  a  coil  of  large  copper  wire,  or, 
better,  of  copper  ribbon,  covered  with 
some  non-conducting  substance,  and 
having  binding  screws  attached  to 
each  end,  to  receive  the  polar  wires 
of  the  battery.  Above  this  is  placed 
a  coil,  W,  of  fine  covered  wire,  with 
a  metallic  handle  at  each  end;  and 
when  the  battery  current  is  made  to 
pass  through  the  lower  coil,  the 
secondary  current  will  be  induced 
in  the  upper  coil,  as  will  be  plainly 
indicated  by  grasping  the  handles  with  the  moist  hands.  In  this 
case,  as  before,  the  secondary  current  is  induced  at  the  moment 
the  battery  current  is  established,  in  the  direction  opposite  that 
of  the  battery  current,  and  again  when  the  battery  current  ceases 
in  the  same  direction  as  this  latter  current. 

The  former  is  termed  the  initial  and  the  latter  the  terminal 
secondary  current. 

The  effect  of  the  shocks  will  be  increased  by  rapidly  breaking 
and  closing  the  battery  circuit,  the  feeble  intensity  of  the  shocks 
being  compensated  by  their  frequency. 

Of  the  two  coils  above  used,  it  is  to  be  observed,  that  the  one 
connecting  the  poles  of  the  battery  is  made  of  large  wire,  or 
ribbon  of  metal,  and  is  of  moderate  length,  while  the  other,  in 
which  the  secondary  current  is  to  be  induced,  is  made  of  smaller 
wire,  and  is  of  much  greater  length.  The  secondary  current  in 
this  case  is  one  of  considerable  intensity  (100),  as  is  shown  by  the 
fact  that  it  can  be  made  to  pass  through  the  system ;  but  if  the 
coil  had  been  made  of  a  large  wire,  and  much  shorter  than  it  is, 
the  current  induced  would  have  had  only  a  feeble  intensity,  but 
would  have  been  much  greater  in  quantity.  And,  in  general,  it 
is  found  that  long  coils  of  small  wire  give  secondary  currents  of 

QUESTIONS. — Describe  the  .mode  of  obtaining  a  secondary  current,  as 
illustrated  in  the  next  figure.  When  only  is  this  secondary  current 
induced?  What  are  the  terms  used  to  indicate  these  currents?  What 
rs  their  direction  as  compared  with  the  primary  current?  What  is  said 
of  the  two  coils  used  in  this  experiment? 


130 


ELECTRO-MAGNETISM. 


great  intensity,  while,  on  the  other  hand,  to  obtain  a  current  of 
quantity  short  coils  of  large  wire  or  ribbon  are  required. 

By  arrangements  altogether  similar  to  the  above,  with  addi- 
tional coils,  tertiary  currents  have  been  produced,  and  others  of 
gtill  higher  orders,  even  up  to  the  seventh  or  ninth. 

The  following  mode  of  developing  the  tertiary  current  will  show 
the  method  to  be  pursued  to  obtain  others  of  still  higher  orders. 
A  is  a  ribbon  coil  through  which  the  battery  current  revolves  as 
before,  and  B  another  ribbon  coil  in  which  a  secondary  current  is 
induced,  as  already  explained.  A  third  ribbon  coil,  C,  is  placed 
at  a  little  distance,  but  has  its  two  ends  connected  by  means  of 
wires  with  the  two  ends  of  the  ribbon  of  the  coil  B,  so  that  the 
same  current  which  is  induced  in  B  flows  also  in  C.  Above  C  is 
placed  an  intensity  coil  of  small  wire,  W,  with  metallic  handles 
connected  with  its  extremities.  Now  when  the  battery  current  is 
established  in  the  coil,  A,  a  secondary  current  is  induced  in  B  and 
revolves  in  the  coil,  C,  by  which  a  tertiary  current  is  induced  in 
the  coil  W.  As  the  secondary  current  flows  in  the  opposite 


Tertiary  Current. 

direction  from  that  of  the  battery  current,  so  the  tertiary  takes 
the  opposite  direction  from  that  of  the  secondary ;  and  the  same 
law  holds  good  through  all  the  series  of  currents.  As  the  dis- 
tance from  the  battery  increases,  the  strength  of  the  current 
gradually  diminishes. 


QUESTIONS. — Describe  the  mode  of  obtaining  a  tertiary  current.  What 
is  said  of  the  direction  of  the  tertiary  current  as  compared  with  that  of 
the  secondary  current  ? 


ELECTRO-MAGNETISM.  131 

143.  Induction  of  Electricity  by  Magnetism— Magneto- 
Electricity. — Magneto-electricity,  as  the  term  implies,  is  the 
reverse  of  electro-magnetism.  The  current  of  galvanic  electricity 
circulating  around  a  bar  of  soft  iron,  converts  it,  as  we  have  seen, 
into  a  temporary  magnet,  and  renders  a  bar  of  steel  permanently 
magnetic.  Now,  d  priori,  it  would  seem  very  probable  that  a 
magnet  placed  in  the  centre  of  a  helix  or  spiral  of  metallic  wire, 
would  develope  in  it  a  current  of  electricity.  This  is  found  to 
be  actually  the  case ;  but  the  current  can  be  observed  only  at  the 
moment  of  inserting  the  magnet  or  removing  it. 

The  development  of  electricity  by  magnetism  is  shown  in  a 
very  simple  manner,  by  winding  the  middle  of 
the  keeper  or  armature  AB  of  a  powerful  horse- 
shoe magnet,  with  copper  wire,  properly  bound, 
and  bringing  the  two  extremities  of  the  wire  into 
contact,  one  of  which  should  be  flattened  a  little, 
and  amalgamated  by  dipping  it  into  a  solution  of 
nitrate  of  mercury,  and  the  other  filed  to  a  point. 
If,  now,  the  armature  be  suddenly  placed  upon 
the  magnet  or  removed  from  it,  a  spark  of  elec- 
tricity will  manifest  itself  every  time,  at  the  point 
of  contact,  C,  of  the  two  extremities  of  the  wire.  Magneto-Electricity. 

The  electric  current  flows  in  one  direction  at  the  moment 
magnetism  is  induced  in  the  soft  iron  enclosed  in  the  coil 
of  wire,  and  in  the  other  direction,  when  its  magnetism  is 
destroyed. 

The  same  thing  is  accomplished,  but  in  a  manner  a  little  different,  by 
the  apparatus  figured  on  the  next  page.  Externally  a  large  coil  of  fine 
copper  wire  is  seen,  terminating  in  binding  screws,  to  which  wires  with 
handles,  H,  are  attached,  to  be  grasped  by  the  hands.  Within  this  is  a 
smaller  coil  of  larger  wire,  the  top  of  which  is  seen  at  B ;  the  extremities 
of  this  wire  are  soldered  to  the  binding  screws  A  and  D,  the  latter  also 
connecting  with  the  horizontal  bar  E  C,  which  has  an  irregular  surface, 
resembling  that  of  a  coarse  file.  Inside  of  the  last  coil  is  a  bundle  of 
small  iron  wires,  W.  Now  when  the  wires  from  the  battery  are  con- 
nected with  the  binding  screws  A  and  D,  the  current  circulating  in  the 

QUESTIONS. — 143.  What  is  the  term  ma^ne/o-electricity  used  to  signify? 
Poscribe'  the  method  of  developing  electricity  by  means  of  a  permanent 
magnet  and  armature.  Describe  the  apparatus  represented  by  the  next 
figure,  aod  the  mode  of  using  it. 


132 


ELECTRO- MAGNETISM. 


Magneto-Electricity. 


helix  B  induces  magne- 
tism in  the  wires  W,  and 
this  in  turn  at  the  mo- 
ment when  the  magne- 
tism is  induced,  or  when 
it  is  destroyed,  induces 
a  current  of  electricity 
in  the  outer  helix,  which 
will  be  felt  in  the 
hands  when  grasping 
the  handles. 

To  produce  the  great- 
est effect,  the  current 
from  the  battery  should 
be  foriiicd  and  broken 
rapidly;  which  is  accom- 
plished by  connecting 
one  wire  with  the  bind- 
ing screw  A,  and  draw- 
ing theTfend  of  the  other 
over  the  rough  sur- 
face EC. 


144,  Magneto-electric  machines  are  now  made,  which  act  with 
great  energy,  producing  all  the  effects  both  of  quantity  and 
intensity. 


Magneto-Electric  Machine. 


The  above  figure*  represents  a  machine  of  this  kind.  Several 
steel  magnets,  NS,  are  firmly  fixed  together  upon  pillars  on  a 
base  board;  and  in  front  of  the  poles,  an  armature,  A,  in  the 


From  Davis's  Manual  of  Magnetism. 


QUESTION. — 144.  Describe  the  magneto-electric  machine. 


ELECTRO- MAGNET  ISM.  ,  133 

form  of  the  letter  U,  having  its  two  arms  wound  with  2000  or 
3000  feet  of  fine  insulated  wire,  is  made  to  revolve  on  an  axis  by 
means  of  the  multiplying  wheel  W.  As  the  armature  is  made 
to  revolve  in  front  of  the  strong  poles  of  the  fixed  magnets,  mag- 
netism is  induced  in  it  (121),  currents  of  electricity  being  at  the 
same  time  made  to  flow  through  the  coils  of  wire  wound  upon  its 
arms,  in  accordance  with  the  principles  just  explained,  which  are 
communicated  by  wires,  concealed  under  the  base  board,  to  the  me- 
tallic handles,  H,  by  the  wires  C  and  D.  These  currents  being  in  one 
direction  while  the  magnetism  of  the  armature  is  increasing — that 
is,  during  one  quarter  of  each  revolution — and  in  the  other  direction 
while  the  magnetism  is  diminishing,  would  be  scarcely  appreciable 
but  for  a  contrivance  by  which  it  is  constantly  interrupted  and 
renewed.  This  is  accomplished  by  a  toothed  wheel  placed  upon 
the  axis  at  0,  against  which  the  wire  C  constantly  presses,  slip- 
ping from  tooth  to  tooth  as  the  wheel  is  turned.  At  every  inter- 
ruption of  the  current  a  powerful  shock  is  felt  by  any  one  grasping 
the  handles. 

145.  The  Electro-Magnetic  Telegraph.  —  This  is  an  instru- 
ment for  conveying  intelligence  instantaneously,  by  means  of  the 
galvanic  current,  to  any  distance,  where  metallic  wires  can  be 
extended  and  properly  insulated. 

We  have  seen  above  (136),  that  the  current,  when  made  to 
pass  around  pieces- of  soft  iron,  renders  them  magnetic  while  'the 
current  is  passing,  but  that  they  lose  their  magnetism  instantly 
when  the  current  is  interrupted.  Usually,  the  experiment  is  per- 
formed with  the  battery  and  the  piece  of  iron  in  the  same  room, 
and  even  upon  the  same  table,  but  this  is  not  necessary.  If  the 
battery  be  in  one  room,  and  the  piece  of  iron  in  another  room,  or 
in  another  building  at  a  distance,  the  result  will  be  the  same, 
only  a  little  increase  in  the  power  of  the  battery  will  be  neces- 
sary. All  that  is  required  is,  that  good  conducting  wires,  well 
insulated,  should  extend  from  the  battery  and  form  a  helix  around 
the  iron,  and  on  closing  the  circuit,  whatever  may  be  the  distance 

QUESTIONS. — What  is  the  length  of  the  wire  upon  the  revolving  arma 
ture?  What  is  the  use  of  the  toothed  wheel?  145.  What  is  the  electro- 
magnetic telegraph  ?  May  the  current  from  a  battery  be  made  to  magnetize 
a  piece  of  iron  at  a  distance  ?  What  is  required  for  this  purpose  ? 

12 


ELECTRO-MAGNETISM. 


of  the  iron  from  the  battery,  it  instantly  becomes  magnetic,  and 
loses  its  magnetism  again  when  the  circuit  is  broken.  The  closing 
and  breaking  of  the  circuit  can  be  performed  at  any  point  in  the 
line,  but  we  suppose  it  to  be  done  at  the  battery. 


Morse  Telegraph. 

The  above  figure,  which  represents  the  recording  part  of 
Morse's  telegraph,  will  perhaps  serve  better  to  illustrate  the 
operation  of  the  instrument  than  a  full  figure  of  it.  A  piece 
of  soft  iron,  M,  in  the  form  of  the  letter  U,  with  each  arm  sur- 
rounded with  a  helix  of  covered  wire,  is  firmly  fixed  upon  a  base- 
board, with  the  ends  upward,  and  the  extremities  of  the  wires 
of  the  helix  connected  with  the  binding  screws,  (seen  at  the  right,) 
with  which  the  wires  from  the  battery  are  connected.  A  is  an 
armature  of  soft  iron,  fixed  to  the  short  arm  of  a  lever,  which  at 
the  other  end  carries  a  blunt  point  of  steel,  capable  of  indenting 
.  characters  upon  paper  when  pressed  against  it.  Above  the  point 
is  a  metallic  roller,  with  a  groove  cut  around  it,  into  which  the 
point  plays,  and  a  narrow  slip  of  paper  is  supposed  to  be  drawn 
along  between  them  by  the  hand. 

Now  let  us  suppose  this  instrument,  which  we  will  call  the 
register,  to  be  in  New  York,  and  the  battery  in  Washington, 
with  metallic  wires,  well  insulated,  extended  between  them ; 
when  the  operator  in  Washington  closes  the  circuit,  the  iron  M 
instantly  becomes  magnetic,  drawing  down  the  armature  A,  and 
pressing  the  point  at  the  other  extremity  of  the  lever  against  the 
paper,  producing  a  dot  if  the  paper  is  at  rest,  but  a  straight  line 
if  it  is  in  motion.  When  the  operator  in  Washington  breaks  the 

QUESTIONS. — Describe  the  figure  given  to  illustrate  the  recording  part 
of  Morse's  telegraph.  How  is  a  mark  made  upon  the  paper  ?  Describe 
the  mode  in  which  an  operator  in  Washington  may  write  in  New  York. 
What  are  the  only  marks  the  instrument  is  capable  of  making  ? 


ELECTRO- MAGNETISM. 


135 


circuit,  the  iron  M  loses  its  magnetism,  and  the  lever  drops  by  its 
own  weight,  leaving  the  paper  to  move  along  unmarked.  When 
the  circuit  is  again  closed,  the  point  is  raised  again  in  like  man- 
ner against  the  paper,  and  immediately  drops  when  the  circuit  is 
broken ;  so  that  the  steel  point  in  New  York  is  perfectly  under 
the  control  of  the  operator  in  Washington,  for  making  dots  and 
straight  lines,  with  which  an  alphabet  is  easily  constructed.  Thus 
a  dot  and  line  (.  — )  is  A,  a  line  and  three  dots  ( — . .  .)  B,  a  single 
dot  ( . )  E,  and  so  on  through  the  alphabet. 

In  the  next  figure  the  full  instrument  of  Morse  is  represented. 
The  paper,  P,  is  carried  along  by  machinery,  between  two  rollers, 
in  the  direction  indicated  by  the  arrows,  the  machinery  being 
propelled  by  a  weight.  A  spiral  spring,  S,  attached  to  a  piece 
projecting  downward  from  the  pen-lever,  removes  the  steel  point 
from  the  paper  when  the  circuit  is  broken.  W  W,  the  wires  of 


Morse's  Telegraph. 

the  magnet.     The  motion  of  the  machinery  is  regulated  by  a  fan, 
which  is  partly  seen  in  the  figure. 

146.  In  order  to  send  communications  at  the  same  time  from 
New  York  to  Washington,  another  arrangement  similar  to  the 
above  is  needed,  with  the  register  in  Washington ;  but  the  sam 
wires  and  the  same  battery  may  be  used  to  return  an  answer,  after 

QUESTIONS. — How  is  the  alphabet  used  in  this  telegraph  constructed? 
146.  May  the  same  battery  and  the  same  wires  be  made  use  of  to  send 
communications  between  two  places  in  both  directions  ? 


136  ELECTRO-MAGNETISM. 

the  Washington  operator  has  finished,  merely  by  having  a  second 
register  in  the  same  circuit  in  Washington,  and  the  operator  in 
New  York  breaking  and  closing  the  circuit  in  that  place,  as  before 
explained.  Nor  is  it  necessary,  if  the  register  is  in  New  York, 
the  battery  should  be  in  Washington ;  it  may  be  at  any  point  in 
the  circuit. 

In  the  above  explanation,  two  wires  are  supposed  to  be  extended 
the  whole  distance  between  the  places  connected  by  the  telegraph ; 
but  experiment  has  shown  that  only  one  is  really  needed,  as  the 
earth  may  be  made  to  form  a  part- of  the  circuit. 

Besides  the  above,  two  other  electric  telegraphs  are  in  use  in  this 
country,  and  one  or  two  of  still  different  construction  in  Europe. 
House's  telegraph  (from  the  name  of  the  inventor)  is  a  most  ingenious 
instrument,  which  performs  the  wonderful  operation  of  printing  in  dis- 
iinct  capitals  the  messages  transmitted.  It  is  too  complex  to  be  under- 
stood without  a  close  examination  of  the  instrument  itself. 

Bain's  telegraph  is  worked  precisely  like  Morse's,  but  the  marks  are 
made  on  chemically  prepared  paper,  by  transmitting  the  current  of  elec- 
tricity ttirough  it.  Like  Morse's,  also,  it  marks  only  dots  or  straight 
lines. 

QUESTIONS. — Are  more  than  one  wire  needed  to  send  communications 
between  two  places  in  both  directions?  Are  other  telegraphs  besides 
Morse's  in  use  ?  , 


PAKT   II. 

GENERAL   CHEMISTRY. 

147.  THERE  are  two  very  distinct  sub-divisions  of  the  general 
science  of  Chemistry,  usually  denominated  Inorganic  Chemistry, 
and  Organic  Chemistry;  the  former  of  which  treats  only  of  the 
chemical  history  of  the  elements  and  their  inorganic  compounds, 
while  the  latter  treats  of  the  chemistry  of  animal  and  vegetable 
bodies.  There  are,  however,  certain  principles  equally  applicable 
to  both  branches  of  the  science,  which  we  propose  first  to  consider, 
under  the  above  head. 


THE    ELEMENTS.  —  CHEMICAL    AFFINITY, 

148.  The  Elements. — We  consider  all  substances  as  simple,  or 
elementary,  that  have  not  been  decomposed.  Of  the  exact  num- 
ber of  these  we  cannot  speak  with  certainty,  as  the  existence  of 
two  or  three,  the  discovery  of  which  has  been  announced,  has  not 
yet  been  sufficiently  verified.  On  a  following  page  will  be  found 
a  list  of  sixty-two,  the  existence  of  which,  it  is  believed,  has  been 
established.  Some  of  these,  as  we  shall  see  hereafter,  are  found 
only  in  very  small  quantities,  while  others  are  abundant,  the 
great  mass  of  the  globe  we  inhabit  being  made  up  of  the  various 
compounds  of  some  fourteen  or  sixteen. 

The  elementary  substances  are  usually  divided  into  the  two 
classes  of  non-metallic  and  metallic,  fifteen  being  included  in 
the  former,  and  the  remainder  in  the  latter  class ;  but  several  of 
each  class  possess  characters  so  peculiar,*  that  it  is  difficult  to 
assign  them  their  proper  place. 

QUESTIONS. — 147.  What  two  sub-divisions  of  the  general  science  of 
Chemistry  are  there  ?  What  is  the  distinction  between  them  ?  Of  what 
is  it  proposed  to  treat  under  the  head  of  General  Chemistry  ?  148.  What 
are  simple  substances  ?  How  many  elements  are  there-?  What  is  said 
of  the  quantities  of  these  afforded  by  nature  ?  What  two  divisions  of 
them  do  we  recognize  ? 

12  *  (137) 


138  AFFINITY. 

149.  Affinity,  —  Affinity,  or  chemical  attraction,  has  already 
been  mentioned  as  one  of  the  forces  with  which  the  particles  of 
every  kind  of  matter  seem  to  be  naturally  endow.ed.     It  is  to  the 
action  of  this  force  that  all  chemical  changes,  and  the  accompany- 
ing phenomena,  are  to  be  attributed.     If  two  elements  unite  to 
form  a  compound,  it  is  this  force  which  occasions  it  j  and  if 'a  com 
pound  of  two  or  more  substances,  already  formed,  is  destroyed  by 
the  action  of  another  element,  it  is  to  this  force  we  are  to  look  for 
the  cause  of  the  change. 

Affinity  is  exerted  only  between  the  minutest  particles  of  dif- 
ferent kinds  of  matter,  causing  them  to  combine  so  as  to  form  new 
bodies,  endowed  with  new  properties.  It  acts  only  at  insensible 
distances ;  in  other  words,  apparent  contact,  or  the  closest  proxi- 
mity, is  necessary  to  its  action.  Every  thing  which  prevents 
such  contiguity  is  an  obstacle  to  combination;  and  any  force 
*which  increases  the  distance  between  particles  already  combined, 
tends  to  separate  them  permanently  from  each  other.  It  follows, 
therefore,  that,  though  affinity  is  regarded  as  a  specific  power,  dis- 
tinct from,  the  other  forces  which  act  on  matter,  its  action  may  be 
promoted,  modified,  or  counteracted  by  them  j  and,  consequently, 
in  studying  the  phenomena  produced  by  affinity,  it  is  necessary  to 
inquire  into  the  conditions  that  influence  its  operation. 

150.  The   most   simple  instance  of  the   exercise  of  chemical 
attraction  is  afforded  by  the  admixture  of  two  substances.     Water 
and  sulphuric  acid,  or  water  and  alcohol,  combine  readily.     On 
the  contrary,  water  shows  little  disposition  to  unite  with  sulphuric 
ether,  and  still  less  with  oil ;  for,  however  intimately  their  particles 
may  be  mixed  together,  they  are  no  sooner  left  at  rest  than  the 
ether  separates  almost  entirely  from  the  water,  and  a  total  separa- 
tion takes  place  between  that  fluid  and  the  oil.     Sugar  dissolves 
very  sparingly  in   alcohol,  but   to   any  extent  in   water;    while 
camphor  is  dissolved  in  a  very  small  degree  by  water,  and  abun- 
dantly by  alcohol.     It  appears,  from  these  examples,  that  chemical 
attraction  is  exerted  between  different  bodies  with  different  degrees 

QUESTIONS. — 149.  What  is  affinity  ?  Are  all  chemical  changes  to  be  re- 
ferred to  this  forqe  ?  Between  what  only  is  it  exerted  ?  Is  it  influenced  in 
its  action  by  other  forces  of  nature  ?  150.  Where  do  we  observe  the  most 
simple  instance  of  the  exertion  of  this  force  ?  Is  it  exerted  with  equal 
intensity  between  all  bodies? 


AFFINITY.  189 

of  force.  There  is  sometimes  no  proof  of  its  existence;  between 
some  substances  it  acts  very  feebly,  and  between  others  with  great 
energy. 

Affinity  is  therefore  said  to  le  elective,  as,  when  several  sub- 
stances, capable  of  combining,  are  mixed  together,  a  particular 
compound  is  always  formed,  in  preference  to  others.  Thus,  if 
sulphuric  acid,  soda,  and  lime  are  at  any  time  mixed  together,  the 
acid  will  always  combine  with  the  lime,  in  preference  to  the  soda. 

151.  Decomposition  of  a  compound  is  often  effected  by  present- 
ing to  it  a  third  substance,  having  a  stronger  affinity  for  one  of 
the  ingredients  of  the  compound  than  those  ingredients  have  for 
each  other.     Thus,  oil  has  an  affinity  for  the  volatile  alkali,  am- 
monia, and  will  unite  with  it,  forming  a  soapy  substance  called 
liniment.     But  the  ammonia  has  a  still  greater  attraction  for  sul- 
phuric acid ;  and  hence,  if  this  acid  be  added  to  the  liniment,  the 
alkali  will  quit  the  oil,  and  unite  by  preference  with  the  acid. 
If  water  be   poured  into  a  solution  of  camphor  in  alcohol,  the 
camphor  will  be  set  free,  because  the  alcohol  combines  with  the 
water.     Sulphuric  acid,  in   like  manner,  separates    baryta  from 
nitric  acid.      Combination  and  decomposition   occur  in  each  of 
these  cases; — combination  of  sulphuric  acid  with  ammonia,  of 
water  with  alcohol,  and  of  baryta  with  sulphuric  acid ; — decom- 
position of  the  compounds  formed  of  oil  and  ammonia,  of  alcohol 
and  camphor,  and  of  nitric  acid  and  baryta. 

The  action  becomes  more  complex  when  two  compounds  are 
presented  to  each  other,  of  such  a  nature  that  a  transfer  of 
elements  takes  place  between  them.  Thus,  in  mixing  a  solu- 
tion of  carbonate  of  ammonia  with  another  of  hydrochlorate 
of  lime,  the  carbonic  acid  of  the  first  compound  unites  with  the 
lime  of  the  second,  while  the  hydrochloric  acid  of  the  second  com- 
bines with  the  ammonia  of  the  first. 

152.  Action  of  Affinity  Modified  by  Circumstances. — The 
action  of  affinity  is  influenced  greatly  by  various  circumstances, 
only  a  few  of  which  can  be  here  noticed. 

QUESTIONS. — Why  is  affinity  said  to  be  elective?  151.  How  is  decom. 
position  effected  by  the  exertion  of  this  force?  Give  an  illustration. 
152.  Is  the  action  of  affinity  modified  by  the  circumstances  in  which  it  is 
exerted  ? 


140  AFFINITY. 

The  particular  state  of  a  substance,  whether  solid,  liquid,  or 
gaseous,  is  a  very  important  circumstance,  intimately  affecting  all 
its  chemical  relations.  It  is  very  rarely  the  case  that  two  solids 
are  capable  of  combining ; — one  of  them  at  least  must  first  be  made 
liquid,  either  by  solution  in  some  solvent,  or  by  melting.  Thus, 
tartaric  acid  and  carbonate  of  soda,  in  a  dry  state,  are  kept  toge- 
gether  for  any  length  of  time,  without  any  action  taking  place 
between  them ;  but  if  a  little  water  be  added  to  dissolve  them, 
chemical  action  at  once  ensues,  attended  with  violent  effervescence. 
Phosphorus  and  iodine,  though  both  are  solids,  and  phosphorus 
and  sulphur,  will  indeed  combine  when  brought  together  in  their 
ordinary  state  j  but  even  in  these  cases,  one  or  both  of  the  sub- 
stances are  made  liquid  during  the  action. 

153.  Cohesion  (for  it  is  this  force  which  unites  the  particles  of 
a  solid)  is  therefore  always  opposed  to  the  action  of  affinity;  and 
whatever  tends  to  diminish  it  in  bodies  capable  of  acting  upon  each 
other,  facilitates  their  union.     Heated  water  is  therefore  usually 
a  more  powerful  solvent  than  when  cold;  and  salt  in  fine  powder 
will  be  dissolved  more  rapidly  in  water,  than  when  in  large 
lumps. 

154.  The  gaseous  state 'is  also  unfavorable  to  the   action  of 
affinity.     Gases  do  indeed,  in  some  cases,  combine  spontaneously, 
but,  usually,  the  introduction   of  an  ignited  body,  the  electric 
spark,  or,  in  some  cases,  the  influence  of  the  sun's  rays,  is  needed 
to  cause  the.  action  to  commence.     Thus,  a  mixture  of  oxygen  and 
hydrogen  may  be  kept  for  any  length  of  time;    but  the  intro- 
duction of  flame,  or  the  passage  of  the  smallest  spark  of  electricity, 
will  cause  them  to  combine  instantly,  with  a  powerful  explosion. 

155.  Contact,  with  a  third  Lody  sometimes  will  cause  a  union 
of  two  elements,  that  would  otherwise  remain  together  without 
combining.     Thus,  the  introduction  of  a  piece  of  spongy  platinum 
into  a  mixture  of  oxygen  and  hydrogen,  produces  an  explosion  in 
a  few  seconds,  without  any  change  being  produced  in  the  metal, 

QUESTIONS. — What  is  said,  in  this  connection,  of  the  peculiar  state  of 
a  substance,  whether  it  be  solid,  liquid,  or  gaseous?  Give  an  example. 
]63.  Is  cohesion  always  opposed  to  affinity?  154.  What  is  said  of  the 
gaseous  state  ?  How  may  gases  that  remain  in  mixture  without  uniting 
afterwards  be  made  to  combine  ?  155.  What  is  catalysis  ? 


AFFINITY.  141 

except  that  it  becomes  intensely  heated.  This  power  of  some 
bodies  to  produce-  chemical  changes,  merely  by  their  presence,  is 
termed  catalysis  (from  the  Greek,  kata,  by,  and  luo,  to  unloose). 

156.  Mechanical   action    also    favors    the    action    of    affinity. 
Thus,  if  a  piece  of  phosphorus  be  wrapped,  with  a  few  crystals 

\of  chlorate  of  potash,  in  a  piece  of  tin  foil  or  strong  paper,  a 
\smart  blow  will  cause  a  violent  explosion.  Common  friction 
matches  are  ignited  by  friction  against  sand-paper,  or  other  hard 
substance. 

157.  Relative  quantity  of  matter  is  the  last  circumstance  we 
mention,  as  affecting  the  action  of  this  force.     What  is  meant  by 
this  may  be  illustrated  by  the  solution  of  common  salt  in  water. 
If  equal  quantities  of  the  salt  are  added  in  succession  to  the  water, 
the  first  portion  will  disappear  in  less  time  than  the  second,  the 
second  in  less  time  than  the  third,  and  so  on.     As  the  relative 
quantity  of  salt  contained  in  solution  increases,  the  action  of  the 
water  becomes  enfeebled,  until  full  saturation  takes  place.     If  a 
large  quantity  of  salt  had  been  added  at  first,  the  full  saturation 
of  the  water  would  have  taken  place  much  more  speedily. 

158.  Action  of  Affinity  always  accompanied  by  a  Change 
of  Properties.— A   change   of   properties,   to    a   greater  or  less 
extent,  always  attends   chemical   action;    but  no  means  are  yet 
known  by  which  we  can  predict  what  any  of  these  changes  will  be 
in  any  case,  previous  to  making  the  trial. 

Often,  when  two  bodies  unite,  the  characteristic  properties  of 
both  will  disappear,  and  the  bodies  are  said  to  neutralize  each 
other.  Thus,  the  acids  are  usually  sour  to  the  taste,  and  possess 
the  power  of  changing  the  blue  color  of  some  vegetables  to  red; 
while  the  alkalies  are  exceedingly  caustic  to  the  taste,  and  change 
vegetable  blues  to  green.  Now,  when  an  acid  and  an  alkali 
unite,  a  new  substance  is  formed,  called  a  salt,  which  is  mild  to 
the  taste,  and  produces  no  eifect  whatever  upon  vegetable  colors; 

QUESTIONS. — 156.  What  is  said  of  mechanical  action?  Give  an  illus- 
tration. 157.  What  is  said  of  the  relative  quantities  of  matter  that  are 
brought  to  act  upon  each  other?  Give  an  illustration.  158.  Does  a 
change  of  properties  usually  accompany  chemical  action?  Can  we  from 
a  knowledge  of  the  substances  used,  predict  before  trial  what  the  changes 
•will  be  ?  When  are  substances  said  to  neutralize  each  other  ?  Give  an 
illustration. 


142  AFFINITY. 

and,  indeed,  while  it  possesses  many  new  properties  of  its  own, 
it  exhibits  none  of  those  of  either  of  its  ingredients. 

159.  This  change  may  extend  to  any  or  all  of  the  properties 
of  bodies.  (1.)  Bodies,  after  combining,  do  not  usually  occupy 
the  same  space  as  they  did  before  combination.  Generally,  a  con- 
traction of  volume  takes  place,  but  this  is  not  universal.  •  A  pint 
of  water,  added  to  a  pint  of  sulphuric  acid,  will  not  produce  a 
quart  of  the  mixture;  and  the  same  will  be  found  true  of  water 
and  alcohol.  When  two  gases  combine,  a  very  great  contraction 
often  takes  place ;  but  the  result  with  different  gases  is  very  dif- 
ferent. (2.)  The  changes-  of  form  that  attend  chemical  action  are 
exceedingly  various.  The  combination  of  gases  may  give  rise  to 
a  liquid,  as  in  the  union  of  oxygen  and  hydrogen  to  form  water ; 
or  to  a  solid,  as  in  the  union  of  carbonic  acid  gas  and  ammonia  to 
form  solid  carbonate  of  ammonia ;  or  hydrochloric  acid  and  am- 
monia, to  form  hydrochlorate  of  ammonia.  Two  solids  may,  in 
combining,  form  a  liquid,  as  is  the  case  when  crystals  of  sulphate 
of  soda  and  nitrate  of  ammonia  are  rubbed  together  in  a  mortar, 
or  acetate  of  lead  ajid  alum.  Solids  may  also,  in  combining,  form 
gases,  as  is  the  case  when  gunpowder  detonates.  Two  liquids,  by 
uniting,  may  form  a  solid,  as  may  be  shown  by  pouring  sulphuric 
acid  into  a  solution  of  hydrochlorate  of  lime.  (3.)  Chemical 
action  is  frequently  attended  by. change  of  color.  No  uniform 
relation  has  been  traced  between  the  color  of  a  compound  and  that 
of  its  elements.  Iodine,  whose  vapor  is  of  a  violet  hue,  forms  a 
beautiful  red  compound  with  mercury,  and  a  yellow  one  with 
lead.  The  black  oxide  of  copper  generally  gives  rise  to  green 
and  blue-colored  salts';  while  the  salts  of  the  oxide  of  lead,  which 
is  itself  yellow,  are  for  the  most  part  colorless. 

A  beautiful  instance  of  the  change  of  color  produced  by  chemical  action 
is  seen  in  mixing  solutions  of  chloride  of  mercury  and  iodide  of  potas- 
sium. The  solutions  may  be  made  as  perfectly  limpid  as  water,  but, 
upon  being  mixed,  a  beautiful  vermilion  red  is  produced,  by  the  forma- 
tion of  iodide  of  mercury.  The  color  shortly  disappears,  if  either 
Bolution  was  in  excess,  by  the  redissolving  of  the  precipitate.  About 
27  parts  of  the  chloride  should  be  used  with  33  parts  of  the  iodide. 

QUESTIONS. — 159.  May  the  change  extend  to  all  the  properties  of  bodies ! 
Give  some  illustrations. 


COMBINATION.  143 


LAWS    OF    COMBINATION. — ATOMIC    THEORY. 

160.  Laws  of  Combination. — The  relative  proportions  in  which 
substances  unite  to  fomi  the  different  compounds,  is  governed  by 
fixed  laws.     There  are,  however,  some  apparent  exceptions  to  this 
rule,  in  which  bodies  seem  to  unite  in  all  proportions,  without 
reference  to  any  law.     Thus,  water  and  alcohol  seem  to  unite  in 
all  proportions ;  and  the  same  may  be  said  of  water  and  the  liquid 
acids.     There  are  still  other  substances  which  seem  to  combine  in 
any  proportion  within  certain  limits.     Thus,  water  dissolves  com- 
mon salt  very  readily,  but  the  quantity  ib  is  capable  of  holding  in 
solution  cannot  exceed  about  four-tenths  of  its  own  weight.     Below 
this  limit,  the  water  and  salt  appear  to  unite  in  every  proportion. 

161.  The  following  are  the  laws  which  regulate  the  composition 
of  such  compounds  : — 

I.     The   composition   and   properties  of  compound  bodies   are 

unchangeable. 

By  this  it  is  meant  (1.)  that  any  compound,  while  it  retains  its 
characteristic  properties,  must  contain  the  samfe  elements,  united 
in  the  same  proportions ;  and  (2.)  that  while  a  compound  contains 
the  same  elements,  united  in  the  same  proportion,  it  must  also 
possess  the  same  characteristic  properties.  Thus,  water,  a  com- 
pound of  1  part*  of  hydrogen  and  8  parts  of  oxygen,  possesses 
certain  well-known  properties;  now,  whenever  and  wherever  a 
substance  is  found,  possessing  the  various  properties  of  water,  we 
know,  from  this  law  that  it  must  be  a  compound  of  these  two  sub. 
stances,  united  in  the  above  proportion ;  and  whenever  a  compound 
of  these  substances,  in  this  proportion,  is  formed,  it  must  possess 
the  peculiar  properties  of  water. 

A  change  of  properties  always  necessarily  implies  a  change  of 
composition ;  and,  conversely,  a  change  of  composition  necessarily 
implies  a  change  of  properties.  This  law  is  of  universal  applica- 
tion, except  in  the  case  of  isomeric  compounds,  which  will  be 
hereafter  noticed. 

*  Parts  by  weight  are  always  intended,  unless  it  is  otherwise  expressed. 

QUESTIONS. — 160.  Are  the  relative  proportions  in  which  bodies  com- 
bine governed  by  any  law?  What  example  is  mentioned?  161.  State 
the  first  law  of  combination.  What  is  water  composed  of?  Does  ft 
change  of  properties  always  imply  a  change  of  composition  ? 


144  COMBINATION. 

II.  When  any  substances  (as  _B,  C,  D,  &c.}  combine  with  a  given 
quantity  of  another  substance  (J.),  then  the  numbers  which 
represent  the  proportions  in  which  J3,  C,  D,  &c.,  combine  with 
Ay  will  also  represent  the  proportions  in  which  they  will  com- 
bine with  each  other,  if  such  combinatiofcbe  possible. 

This  law  is  also  of  universal  application,  and  examples  to  illus- 
trate it  arc  abundant.  Thus, 

8-0  parts  of  oxygen    ~| 
•  35-4        "         chlorine  j 

16-0       "         sulphur    j-  combine  \vitli  1  p&rt  of  hydrogen. 
127-0        "         iodine 

80-0        "         bromine  J 

It  follows,  therefore,  that  if  oxygen  and  chlorine  combine,  it  will 
be  in  the  ratio  of  8  parts  of  the  former  to  854  parts  of  the  latter; 
and  if  chlorine  and  iodine  combine,  the  compound  will  contain 
854  parts  of  the  former,  and  127  parts  of  the  latter;  and  so 
of  the  other  substances  mentioned. 

But  it  is  more  common,  as  oxygen  unites  with  nearly  all  other 
substances,  to  determine  the  quantities  severally  of  these  which 
combine  with  8  parts  of  this  element.  Thus, 


16-0  parts  of  sulphur 


35-4 

1-0 

6-0 

14-0 

39-1 

31-0 


chlorine 

hydrogen 

carbon 

nitrogen 

potassium 

phosphorus 


>  combine  with  8  parts  of  oxygen. 


Any  other  substance,  having  an  extensive  range  of  affinity, 
might  also  be  selected  tis  the  basis  of  our  table,  and  the  results 
would  be  the  same.  The  numbers  thus  obtained  for  the  various 
substances  are  called  their  combining  numbers,  equivalents,  or 
atomic  weights.  It  will  be  noticed  that  the  numbers  used  merely 
express  the  relative  quantities  of  the  substances  they  represent, 
that  combine  together;  it  is  therefore  in  itself  immaterial  what 
figures  are  employed  to  express  them.  The  only  essential  point 
s,  that  the  relation  should  be  strictly  observed.  Thus,  the  equiva- 
jtent  of  hydrogen  may  be  assumed  as  10;  but  then  the  number 
for  oxygen  will  be  80;  that  for  chlorine  354,  &c.  Hydrogen 

QUESTIONS. — State  the  second  law  of  combination.  Give  an  example 
in  illustration.  What  are  the  combining  numbers,  equivalents,  or  atomic 
weights  of  substances  ? 


C  0  M  B  I  N  A  T  I  O  N  . 


14.5 


combines  with  other  bodies  in  a  lower  proportion  than  any  other 
known  substance,  and  is  therefore,  with  propriety,  made  tho  unit 
by  most  writers  in  the  English  language;  but  on  the  continent 
of  Europe,  oxygen  is  usually  considered  as  100,  and  the  tables 
constructed  accordingly. 

162.  We  give  below  a  table  of  all  the  known  elementary  sub- 
stances, with  their  combining  numbers,  or  equivalents,  the  com- 
bining weight  of  hydrogen  being  considered  as  the  unit.  To  find 
the  corresponding  numbers  in  a  table  in  which  the  combining 
weight  of  oxygen  is  made  100,  it  is  only  necessary  to  multiply 
the  numbers  in  this  table  by  12-5.  We  insert  also,  in  the  table, 
the  symbols  by  which  the  elements  are  represented  in  chemical 
formulae,  a  subject  to  which  the  attention  of  the  student  will  be 
called  in  a  future  paragraph. 

TABLE  OF  ELEMENTS,  WITH  THEIR  EQUIVALENTS  AND  SYMBOLS. 


Elements. 

Sym- 
bols. 

Equiva- 
lents. 

Elements. 

Sym- 
bols. 

Equiva- 
lents. 

Al 

13-7 

Mo 

460 

Antimony  (Stibium)  

Sb 

129-0 

Nickel  £  

Hi 

29-5 

Arsenic  

As 

75-0 

Nitrogen  

N 

14-0 

Ba 

68-5 

No 

? 

Bismuth 

Bi 

208-0 

Os 

99-5 

ISoron  

B 

10-9 

Oxygen  

0 

8-0 

Br 

800 

Palladium  

Pd 

53-2 

Cd 

560 

Pe 

» 

Calcium 

Ca 

200 

p 

31-0 

c 

6*0 

Platinum 

Pt 

99-0 

Ce 

47-0 

K 

39-1 

Cl 

354 

R 

52-2 

Cr 

26-7 

Ru 

52-2 

Cobalt                 

Co 

29-5 

Se 

39-5 

Cb 

? 

Silicon 

Si 

21-3 

Cu 

31-7 

Ae 

1080 

Di 

48-0 

Na 

23'0 

E 

? 

Sr 

44-0 

F 

19-0 

g 

16-0 

G 

4-7 

Tantalum  

Ta 

184-0 

Gold  (Aurum)"    

Au 

1980 

Te 

64-1 

H 

ro 

Tb 

? 

Iodine 

I 

127-Q 

Th 

59.4 

Iridium 

Ir 

99-0 

Sn 

58-0 

Fe 

280 

Titanium  

Ti 

25-0 

La 

47-0 

Tungsten  (Wolfram)  

W 

92-0 

Pb 

103-5 

u 

60'0 

L 

6-5 

v 

68-5 

MR 

12-0- 

Yttrium  

Y 

32  2 

Mn 

28-0 

Zinc    

Zn 

32-5 

Mercury  (Hydrargyrum).. 

HK 

100-0 

Zirconium  „..  

Zr 

34-0 

QUESTIONS. — 162.    What  are   contained   in   the   table  on  this  page? 
What  is  taken  as  the  unit?     How  may  the  numbers  given  in  the  table  be 
converted  into  others,  in  which  the  combining  weight  of  oxygen  is  100? 
13 


146  COMBINATION. 

Besides  the  preceding  sixty-two  elements,  the  existence  of  which 
seems  to  be  well  established,  the  discovery  of  four  others  has  been 
announced,  which  are  to.  be  considered  as  doubtful.  The  names  Ari- 
dium,  Donarium,  Ilmenium,  and  Thalium  have  been  given  to  them. 

The  equivalents  given  in  the  table  have  been  taken  chiefly  from 
Dana's  table,  found  in  the  last  edition  of  his  Mineralogy,  but  are  reduced 
'to  the  hydrogen  standard.  In  some  few  instances  preference  has  been 
given  to  Regnault's  numbers. 

III.  When  two  substances  combine  in  more  proportions  than  one, 
then  these  different  proportions  will  always  sustain  some  simple 
ratio  to  each  other. 

To  illustrate  this  law,  let  A  and  B  be  two  substances  capable 
of  combining  with  each  other  in  several  proportions ; — the  lowest 
proportion  in  which  they  combine  will  be  in  the  ratio  of  one 
equivalent  of  each-,  or  1  A  +  1  B,  The  other  compounds  they 
form  will  be  of  the  character,  1  A +  2  B,  1 A  +  3  B,  1  A +4  B,  &c.; 
that  is,  1  equivalent  of  one  substance  will  be  united  with  2  or  3, 
or  some  exact  number  of  equivalents  of  the  other  substance. 

The  compounds  of  nitrogen  and  oxygen  afford  an  excellent 
illustration  of  the  above  law.  Thus,  the 

1st  compound  contains — Nitrogen,  14,  and  Oxygen,  8. 
2d         "  "  Do.      14,    "        Do.     16. 

3d         "  "  Do.      14,    "        Do.     24. 

4th       "  "  Do.      14,    «        Do.     32. 

6th       "  "  Do.      14,    "        Do.     40. 

The  law,  however,  admits  of  a  more  general  application  than  these 
examples  alone  would  authorize  us  to  expect.  Substances  may  com- 
bine— and  instances  of  the  kind  are  not  unfrequent — in  the  ratio  of  2 
equivalents  of  the  first  to  3  or  5,  &c.,  equivalents  of  the  second;  and 
even  more  complex  ratios  than  these  are  known,  as  3  equivalents  of  one 
substance  to  4,  5  or  7  of  the  other,  but  they  are  not  common.  They 
may  be  expressed  thus,  2  A  -f  3  B,  2  A  -f  5  B,  &c.,  and  3  A  -f  4  B, 
3  A  -f  5  B,  &c. 

Man'ganese  and  oxygen  combine  in  five  different  proporti6ns,  as  shown 
below.  The  second  compound,  it  will  be  observed,  contains  2  equivalents 
of  the  metal  to  3  equivalents  of  oxygen,  while  the  fifth  contains  2  equiva- 
lents of  the  metal  to  7  equivalents  of  oxygen.  Thus,  the 

1st  compound  contains — Manganese,  28,  and  Oxygen,  8. 
2d         "  "  Do.          56,    "        Do.    24. 

3d        "  "  Do.          28,    "        Do.     16. 

4th       "  "  Do.          28,    "        Do.     24. 

5th       «  «  Do.          56,    "         Do.     56, 

QUESTIONS. — State  the  third  law  of  combination.  Give  an  illus- 
tration. 


COMBINATION:  147 

These  complex  ratios  may  be  expressed  fractionally;  thus,  the 
expressions  2  A  +  3  B,  2  A  +  7  B,  and  3  A  -f  4  B,  are  equal 
respectively  to  1  A  +  1£  B,  1  A  +  3  J  B,  1  A  +  |  B. 

In  the  manganese- series  above  given  one  place,  it  will  be  seen, 
is  wanting,  between  the  fourth  and  fifth,  which  may  hereafter  be 
filled  by  farther  research. 

IV.  The  equivalent  of  a  compound  substance  will  always  & 
equal  to  the  sum  of  the  equivalents  of  the  substances  which 
compose  it. 

Thus,  water  is  composed  of  1  equivalent  .of  oxygen  8,  and  1 
equivalent  of  hydrogen  1;  its  combining  number,  or  equiva- 
lent, will  therefore  be  (8  +  1  =  )  9.  So,  also,  sulphuric  acid, 
which  contains  1  equivalent  of  sulphur  (16)  and  3  equivalents 
of  oxygen  (8x3  =  24),  has  for  its  equivalent  40. 

The  same  is  true  of  all  compound  bodies,  as  hydrochloric  acid, 
which  contains  1  equivalent  of  chlorine,  35-4,  and  1  equivalent 
of  hydrogen,  1,  giving  for  its  equivalent  364.  The  equivalent 
of  potassium  is  39-1,  and  as  this  combines  with  8  of  oxygen  to 
form  potassa,  the  equivalent  of  the  latter  is  47'1  =  39-1  +  8. 
Now,  when  any  compound  substances  unite  with  each  other,  one 
equivalent  of  one  substance  combines  with  one,  two,  or  three 
equivalents  of  the  other  substance,  precisely  as  in  the  case  of  the 
elements.  Thus,  the  hydrate  of  potassar  composed  of  potassa 
and  water,  contains  exactly  1  equivalent,  47-1  parts  of  potassa 
and  1  equivalent,  or  9  parts  of  water;  and  its  equivalent  is 
56-1  =47-1  +  9.  So  the  sulphate  of  potassa  is  composed  of  40 
parts  of  sulphuric  acid  and  47 •!  parts  of  potassa,  having  for  its 
equivalent  87'1;  and  the  nitrate  of  potassa,  composed  of  nitric 
acid  and  potassa,  contains  54  parts  of  the  acid  and  47-1  parts  of 
potassa,  its  equivalent  being  101-1. 

V.  The  quantities  of  gaseous  substances,  estimated  by  measure, 
which  enter  into  combination,  bpar  some  simple  ratio  to  each 
other ,  and  also  the  quantities  of  the  resulting  compounds,  con- 
sidered a*  gaseous,  bear  some  simple  ratio  to  the  sum  of  the 
volume  of  the  ingredients. 

Water,  we  have  seen,  is  composed  of  1  equivalent  (estimated 
ly  weight)  of  each  of  its  elements,  hydrogen  and  oxygen,  which 

QUESTIONS.— State  the  fourth  law.     What  illustration  is  given  ? 


148  COMBINATION. 

are  gases ;  but  if  we  measure  them  before  causing  them  to  com- 
bine, we  shall  find  that  1  pint  of  oxygen  will  unite  with  exactly 
2  pints  of  hydrogen.  If  we  use  more  oxygen  than  this  iu  pro- 
portion, a  part  of  it  will  remain  after  combination ;  and  if  we  use 
less,  a  part  of  the  hydrogen  will  be  left. 

So,  a  pint  of  chlorine  will  combine  with  exactly  a  pint  of 
hydrogen,  and  a  pint  of  nitrogen  with  exactly  3  pints  of  hydro- 
gen form  ammonia ;  and  so  of  other  gaseous  substances,  or  any 
capable  of  taking  this  form,  as  sulphur  or  mercury. 

If  we  represent  the  combining  volume  of  oxygen  by  1,  as  is 
usual,  then  the  combining  volume  of  each  of  the  following  sub« 
Stances,  viz.,  hydrogen,  mercury,  nitrogen,  chlorine,  iodine,  and 
bromine,  will  be  2.  Phosphorus  and  arsenic  have  the  same 
combining  volume  as  oxygen,  1 ;  while  that  of  sulphur  is  £. 

These  numbers  are  determined  by  experiment  precisely  as  the 
numbers  representing  the  proportion  in  which  substances  combine 
by  weight. 

It  follows  from  the  above  that  there  must  be  a  close  relation 
between  the  atomic  weights,  the  combining  volumes,  and  the 
densities  of  gaseous  substances.  The  atomic  weights  of  oxygen 
and  hydrogen,  we  have  seen,  are  as  8  to  1,  while  their  combining 
volumes  are  1  to  2;  it  follows,  therefore,  that  the  density  of 
oxygen  must  be  to  that  of  hydrogen  as  16  to  1.  So  the  atomic 
weights  of  chlorine  and  hydrogen  are  as  354  to  1,  but  they  com- 
bine in  equal  volumes;  their  comparative  densities  must  there- 
fore be  as  their  atomic  weights,  that  is,  as  354  to  1.  In  fact,  in 
all  cases  in  which  the  gases  combine  in  equal  volumes,  their 
densities  respectively  must  be  as  their  atomic  weights.  And  in 
the  cases  of  those  which  do  not  combine  in  equal  volume,  the 
simple  ratio  of  the  combining  volume  being  observed,  it  is  easy  to 
calculate  their  relative  densities  from  their  atomic  weights.  Thus 
the  combining  volumes  of  hydrogen  and  sulphur  vapor  are, 
respectively,  2  and  -i,  and  their  atomic  weights  1  and  16 ;  the 

QUESTIONS. — State  the  fifth  law  of  combination.  What  illustration  is 
given?  Is  there  any  relation  between  the  atomic  weights,  combining 
volumes,  and  densities  of  gaseous  bodies  ?  How  is  this  illustrated  by 
reference  to  oxygen  and  hydrogen?  When  the  combining  volume?  ;:nd 
atomic  weights  of  gases  are  given,  may  their  relative  densities  be  calcu- 
lated t  How  is  this  illustrated  by  reference  to  sulphur  and  hydrogen  ? 


COMBINATION. 


149 


density  of  sulphur  vapor,  compared  with  that  of  hydrogen,  must 
therefore  be  96,  which  is  very  nearly  the  same  as  it  is  found  to  he* 
by  direct  experiment. 

It  is  customary  to  refer  the  densities  of  gaseous  bodies  to  that  of  atmo-. 
spheric  air  (at  a  given  temperature  and  pressure)  taken  as  unity  ;  and 
we  have  then,  as  the  result  of  very  many  experiments,  the  numbers  in 
the  table  below.  These  numbers  will  be  of  use  hereafter. 


One  volume  of  Air  weighs 1-000 

"  "          Hydrogen  weighs    -069 

«  "         Oxygen          "        1-106 

"  "         Nitrogen        «          -971 

«  "         Chlorine        "       2-440 


One  vol.  of  Iodine  vapor  weighs 8-716 

«  .     "      Bromine  "          "  5-400 

«        «      Mercury  «          "  6-976 

«.       "      Sulphur  "          «  6-654 

"        "      Phosphorus  vapor  weighs    4-326 
«        «      Arsenic  "          "       10-370 


By  the  second  part  of  the  fifth  law,  as  enunciated  above,  the' combining 
volumes  of  compound  gases  will  bear  a  simple  ratio  to  the  sums  of  the 
volumes,  of  their  respective  ingredients.  In  some  cases,  no  change  of ! 
volume  takes  place  when  gases  combine,  as  in  the  case  of  chlorine  and 
hydrogen,  where  equal  volumes  combine  and  produce  two  volumes  of 
hydrochloric  acid ;  but  more  frequently  a  change  of  volume  is  observed, 
as  in  the  case  of  vapor  of  water,  which  is  composed  of  1  vol.  of  oxygen  and 
2  vols.  of  hydrogen  condensed  to  2  vols.  of  steam.  So  ammonia  is  a 
compound  of  1  vol.  of  nitrogen  and  3  vols.  of  hydrogen  condensed  into  2 
vols.  of  ammonia. 

The  density  of  a  compound  gas  may  therefore  often  be  calculated  from 
the  density  of  its  ingredients  and  the  change  of  volume  known  to  take 
place  in  combination.  Thus,  in  the  case  of  water,  which  we  have  seen 
is  composed  of  1  vol.  of  oxygen  and  2  vols.  of  hydrogen  condensed  into  2 
vols.  of  steam, 

1  vol.  of  Oxygen  =  1-106 

2  "       Hydrogen  =  2  X  '069  =0-138 


Steam 


1-244 


One-half  of  this  sum,  1-244,  or  0-622,  is  therefore  the  weight  of  1  vol., 
or,  in  other  words,  the  density  of  steam.  This  is  the  same  as  found  by 
direct  experiment.  So  in  the  case  of  ammonia,  mentioned  above, 

3  vols.  of  Hydrogen  =  3  x  "069  =  0-207 
1       "        Nitrogen    —  0*971 


Ammonia 


1-178 


As  this  forms  2  vols.  of  ammonia,  one-half  of  the  sum,  1-178,  or,  -589 
is  the  weight  of  1  vol.,  or  the  density  of  this  compound  gas. 

We  add  one  more  instance,  by  way  of  illustration.      Hydrosulphurio 


QUESTIONS. — Does  a  change  of  volume  sometimes  take  place  when 
gases  combine  ?     How  is  this  illustrated  in  the  case  of  water?     May  the 
density  of  a  compound  gas  be  calculated  from  the  densities  of  its  ingre- 
dients and  the  change  of  volume  that  takes  place  when  they  combine  ? 
13* 


150  ATOMIC    THEORY. 

acid  is  a  compound  of  a  single  equivalent  of  hydrogen  and  sulphur,  the 
Combining  volume  of  the  former  being  1,  and  that  of  sulphur  £.     Now, 

1  vol.  of  Sulphur  vapor  =  6-654 

6      "      Hydrogen  —  6  x  0.069  =     -414 

6       "       Hydrosulphuric  acid       =  7-068 

As  the  7  vols.  in  combining  form  but  6  vols.  of  the  gas,  the  sum  7  068 
is   to   be    divided   by  6,    giving  us  for  the  density  of  hydrosulphuri 
acid,  1-178. 

Some  substances,  as  carbon,  cannot  by  any  means  yet  known  be 
obtained  in  a  state  of  vapor ;  still  we  may  with  some  certainty  calculate 
what  the  density  of  their  vapor  would  be  if  vaporization  were  possible. 
Thus,  in  the  case  of  carbon,  assuming  that  carbonic  acid  is  composed  of 
1  volume  of  carbon  vapor  and  2  volumes  of  oxygen,  the  whole  condensed 
in  2  volumes,  we  have — 

2  vols.  of  Carbonic  Acid         =  2  x  1'524  =  3-048 
2       "        Oxygen  (subtract)  =  2  X  1*106  =  2-212 

1       "        Carbon  vapor  -836 

One  volume  of  carbonic  acid  we  know  contains  1  volume  of  oxygen, 
but  whether  the  carbon  vapor  should  be  taken  as  1  volume  or  only  $  of  a 
volume,  we  have  no  means  of  determining,  except  the  analogy  of  other 
compound  gases,  and  therefore  our  assumption  above  may  not  be  correct. 
It  is  possible  that  carbonic  acid  may  have  a  more  complex  organization 
and  carbon  a  very  different  combining  volume. 

The  combining  volume  of  oxygen  being  taken  as  1,  those  of  all  the 
elementary  bodies  capable  of  assuming  the  gaseous  form  are  1,  2,  or  4, 
except  that  of  sulphur,  "which  is  £.  Of  the  very  many  compound  gases 
whose  combining  volumes  have  been  determined,  that  of  nearly  every 
one  is  either  2  or  4. 

163.  Atomic  Theory. — It  will  be  observed  that  nothing  theo- 
retical pertains  to  the  above  laws,  which  are  simply  the  enuncia- 
tion of  well-determined  facts;  but  such  striking  results,  obtained 
by  experiment,  naturally  incline  us  to  inquire  for  their  cause  ; 
and,  in  the  absence  of  positive  proof,  the  atomic  theory  has  been 
proposed  for  this  purpose. 

This  theory  assumes  that  every  simple  substance  is  an  aggre- 
gation of  atoms  (9),  by  which  is  meant  the  particles  in  their 
smallest  state  of  division ;  and  that  the  atoms  of  the  same  sub- 
stance are  all  precisely  of  the  same  weight.  It  assumes,  also, 
that  when  simple  substances  combine  to  form  compounds,  they 
unite  by  atoms;  that  is,  one  atom  of  one  substance  combines  with 
oue,  two,  three,  &c.,  atoms  of  the  second;  or  two  atoms  of  the 

QUESTION.— 163.  Explain  the  atomic  theory. 


NOMENCLATURE.  151 

first  combine  with  three,  five,  or  seven,  &c.,  atoms  of  the  second, 
£c.  As  these  atoms  are  supposed  to  be  absolutely  indivisible, 
there  can,  of  course,  be  no  such  thing  as  half  an  atom  ]  and  all 
compounds  must  be  of  the  form  1A  +  1B,  1A  +  2B,  2A+3B, 
&c.  The  absolute  weight  of  an  atom  of  any  substance  has  never 
been  determined,  but  it  is  assumed  -that  the  equivalents  of  the 
various  bodies  do  actually  express  their  relative  weights;  the  term 
atomic  weight  is  therefore  often  used  as  synonymous  with  equiva 
lent.  Thus,  the  atomic  weight  of  oxygen  is  said  to  be  8,  and 
that  of  hydrogen,  1,  &c. ;  and  water  is  said  to  be  a  compound  of 
one  atom  of  oxygen  and  one  atom  of  hydrogen ;  while  sulphuric 
acid  is  a  compound  of  one  atom  of  sulphur  and  three  atoms  of 
oxygen — and  so  of  other  compounds. 

Whether  the  assumptions  of  this  theory  are  strictly  true,  we 
may  never  be  able  to  determine  experimentally,  but,  it.  is  readily 
seen,  that  if  they  are  a  correct  expression  of  what  really  takes 
place  in  nature,  they  afford  an  elegant  explanation  of  the  reason 
of  the  above  demonstrated  laws. 

164.  Specific  Heat  of  Atoms. — The  quantities  of  heat  required  to  raise 
the  temperature  of  equal  weights  of  different  bodies  by  a  given  number 
*)f  degrees  (59),  varies  greatly,  according  to  their  nature  ;  and  the  num- 
bers expi-essing  these  quantities,  having  reference  usually  to-water  as 
the  standard,  express  also  the  capacities  for  heat  or  the  specific  heats  of 
these  bodies.  Between  these  numbers  no  special  relation  can  be  traced  ; 
but  if  we  make  the  calculation  in  reference,  not  to  equal  weights,  but  to 
atomic  weights,  then  in  some  nine  or  ten  of  the  elementary  bodies  the 
specific  heats  are  found  to  be  the  same,  while  several  others  have  a  specific 
heat  twice  or  four  times  as  great. 

It  has  been  supposed  that  the  specific  heat  of  the  atoms  of  all  bodies 
may  be  the  same — a  view  which  is  favored  by  the  facts  above  men- 
tioned— but  most  bodies,  both  elementary  and  compound,  depart  so 
widely  from  this  supposed  law  that  its  existence  is  altogether  improbable. 


NOMENCLATURE  OF  CHEMISTRY  —  SYMBOLS. 

165.  Nomenclature. — Chemistry  possesses  a  more  systematic 
nomenclature  than  any  other  branch  of  natural  science ;  and  a 
thorough  knowledge  of  it,  at  the  very  beginning  of  his  studies,  is 

QUESTIONS. — Does  this  theory  account  satisfactorily  for  the  "preceding 
laws  of  combination?  164.  Is  the  specific  heat  of  the  atoms  of  all 
bodies  the  same?  165.  What  is  said  of  the  nomenclature  of  chemistry  ? 


152  NOMENCLATURE. 

very  important  to  the  student.  Thjs  nomenclature  is  framed  in 
reference  to  the  composition  of  compounds,  and  is  so  contrived 
that  the  names  of  all  compounds  shall  indicate  the  substances 
of  which  they  are  composed. 

166.  Elementary  substances  being  composed  of  only  one  kind 
of  particles,  of  course  the  above  remark  does  not  apply  to  them : 
their  names  are  mere  names ;  that  is,  mere  sounds  connected  by 
usage  with  the  things  signified.     Yet,  in  the  case  of  newly  dis- 
covered elements,  names  have  in  some  instances  been  given  that 
indicate  some  important  property  of  the  substance.     Thus,  oxygen 
(from  the   Greek  oxusr  acid,  and  gennao,  to  produce)  was  so 
named,  because  it  was  supposed  to  form  a  necessary  part  of  all 
acids  ;   and  hydrogen  (from  httdor,  water,  and  gennao),  because 
it  was  known  to  enter  into  the  composition  of  water.     So  chlorine, 
being  of  a  greenish  color,  received  its  name,  in  consequence,  from 
the  Greek  chloros,  green ;    and  bromine  was  so  called  from  its 
offensive  odor,  from  bromos,  fetid.     Potassium  and  sodium  are  so 
named,  because  they  form  the  basis,  respectively,  of  potassa  and 
soda;  and  glucinum  (from  glukus,  sweet),  because  of  the  sweet 
taste  of  some  of  its  compounds.     Other  elementary  substances 
of  recent  discovery  have  been  named  in  like  manner;   but  all 
simple  substances  which   have  been   long   known    retain    their 
ancient  names.      Thus,  gold,  silver,  lead,  copper,  sulphur,  car- 
.bon,  are  names  of  well-known  substances,  and  they  are  retained 
in   chemistry;    but  they  contain,   it  is  evident,   no  descriptive 
meaning. 

167.  But  it  is   to    compound   bodies   that  the  nomenclature 
especially  applies;    and,   as   above   intimated,   its    design   is    to 
indicate  their  composition  by  their  names.      For  this  purpose, 
when  two  substances  only  are  combined  in  a  compound,  a  part 
of  the  name  of  one,  with  the  termination  ide,  is  made  use  of, 
while  the  other  is  expressed  in  full.     Thus,  oxygen  forms  oxides ; 
chlorine,  chlorides ;  bromine,  bromides ;  sulphur,  sulphurides,  or 
sulphides;  carbon,  carbonidcs,  or  carbides,  &c.,  of  the  other'sub- 
stance,  the  name  of  which  is  fully  expressed;  as  oxide  of  iron,  oxide 

QUESTION. — In  reference  to  what  is  this  nomenclature  framed  ? 
166.  What  is  said  of  elementary  substances?  167.  How  is  the  tenni< 
nation  ide  used  ?  Give  an  example. 


NOMENCLATURE.  153 

of  sulphur,  cnloride  of  hydrogen,  &c.  Formerly,  usage  required  us 
to  employ  the  termination  ule  for  the  compounds  of  all  the  ele- 
mentary substances  except  those  of  carbon,  sulphur  and  phosphorus, 
with  which,  without  any  apparent  reason,  another  termination,  uret, 
was  used.  Thus,  we  have  been  accustomed  to  say  sulphuret  of 
carbon,  and  not  sulphide ;  phosphuret  of  calcium,  and  not  phos- 
phide; but  a  change  in  this  respect  has  taken  place,  and  the 
termination  ide  is  alone  made  use  of,  as  sulphide  of  carbon,  &c. 

When  two  elements  unite  in  more  than  one  proportion,  numeral 
prefixes  from  the  Greek  or  Latin  are  used  to  designate  them ;  as 
protoxide  of  copper  (from  protos,  first),  and  deutoxide  (deuteros, 
second)  or  binoxide  (bis,  twice)  of  copper.  The  first  of  these 
compounds  contains  one  equivalent  of  oxygen,  united  with  one 
eq.  of  copper,  while  the  second  contains  two  eq.  of  oxygen,  com- 
bined with  one  of  copper.  So  the  teroxide  (tertio,  third)  or 
tritoxide  (tritos,  third)  of  nitrogen,  is  a  compound  of  three  eq. 
of  oxygen  and  one  eq.  of  nitrogen.  The  same  rule  is  observed 
with  regard  to  the- compounds  of  other  substances,  as  protosulphide 
and  bisulphide  of  mercuryj  bicarbofiide  of  sulphur,  terchloride 
of  gold,  £c.  The  prefix  per  is  often  used  to  indicate  the  highest 
compound  known,  as  peroxide  of  lead )  and  the  prefix  sesqui 
implies  that  two  eq.  of  one  of  the  substances  is  combined  with 
three  eq.  of  the  other  substance ;  as  sesqirioxide  of  iron,  which 
contains  two  eq.  of  iron  and  three  eq.  of  oxygen.  Generally,  the 
electro-negative  element  is  expressed  first,  as  chloride  of  sulphur, 
and  not  sulphide  of  chlorine ;  but  this  rule  is  not  universally 
followed. 

168.  Most  of  the  compounds  above  described,  which  may  pro- 
perly be  called  binary,  or  bielementary,  as  being  composed  of  two 
elements,  are  also  capable  of  combining  together,  and  forming 
other  more  complex  compounds,  usually  called  salts.  In  con- 
sidering the  relations  they  sustain  to  each  other,  they  are  usually 
divided  into  the  two  classes  of  acids  and  bases.  The  acids  are 

QUESTIONS. — How  was  the  termination  uret  formerly  used?  When 
two  elements  combine  in  more  than  one  proportion,  how  are  the  different 
compounds  indicated  ?  For  what  is  the  prefix  per  used  ?  Which  element 
is  usually  expressed  first?  168.  May  compounds  combine  to  form  other 
more  complex  compounds  ? 


154  NOMENCLATURE. 

« 

generally  more  or  less  sour  to  the  taste,  change  vegetable  blues 
to  red,  and  are  electro-negative  in  relation  to  the  other  class ; 
while  the  bases  are  electro-positive,  and  restore  the  blue  colors 
which  have  been  changed*  to  red  by  acids.  Some  of  the  bases 
are  soluble  in.  water,  and  are  exceedingly  acrid  and  caustic. 

A  large  proportion  of  all  the  acids  are  oxides,  and  are  there- 
fore called  oxygen  acids,  or  oxyacids ;  but  many  contain  hydrogen, 
and  are  called  hydracids.  So,  when  a  sulphide  possesses  acid  pro- 
perties, it  is  called  a  sulphur  acid. 

As  most  of  the  acids  belong  to  the  first  class,  or  are  oxyacids, 
special  reference  is  had  to  them  in-the  nomenclature ;.  and  they 
are  named  by  using  the  termination  ic  or  ous  in  connection  with 
the  name  of  the  substance  with  which  the  oxygen  is  combined  to 
form  the  acid,  the  termination  ic  being  used  for  the  acid  contain- 
ing most  oxygen,  when  there  are  more  than  one  formed  from  the 
same  substance,  and  the  termination  ous  for  the  one  containing 
least.  Thus  we  have  sulphuric  and  sulphurous  acids,  the  former 
of  which  contains  more  oxygen,  and  is  a  more  powerful  acid  than 
the  latter.  When  there  are  more  than  two  acids  formed  from  the 
same  substance,  the  prefix  "hypo  (Jiupo,  sub,  or  under)  is  used  in 
connection  with  the  name  of  one  or  the  other  of  the  two  already 
described,,  as  the  case  may  require.  Thus,  we  kave  %posulphuric 
acid,  which  contains- less  oxygen  than  the  sulphuric,  and  the 
/i^posulphurous,  which  contains  less  oxygen  than  the  sulphurous. 

When  a  compound,  not  containing  oxygen,  possesses  acid  pro- 
perties, a  part  of  the  name  of  one  of  the  substances  is  used  as  a 
prefix  to  the  name  of  the  other  substance,  to  form  a  name  for  the 
.  acid.  Thus,  hydrochloric  and  hydrosulphuric  acids  are  compounds 
of  hydrogen  with  chlorine  and  sulphur  respectively.  So  chloriodic 
acid  is  a  compound  of  chloride  and  iodine,  Some  writers  are 
particular  to  take  the  prefix  from  the  name  of  the  negative  ele- 
ment, and  say  chlorohydric,  sulphydric,  &c. ;  but  there  is  no  good 
reason  for  such  a  distinction  If  no  prefix  is  used,  the  acid  is 
understood  to  be  an  oxyacid,  as  nitric  acid,  which  is  composed 
of  nitrogen  and  oxygen. 

QUESTIONS. — How  are  acids  generally  characterized  ?  How  are  bases  ? 
What  are  oxyacids  ?  What  hydracids  ?  How  are  the  oxyacids  named  ? 
How  is  the  prefix  hypo  used?  Give  examples.  When  an  acid  compound 
does  not  contain  oxygen  how  is  it  named  ?  Give  examples. 


SYMBOLS.  155 

169.  The   salts   are  compounds  of  the  aeids  with  bases,  as 
Glauber's  salt  (sulphate  of  soda),  which  is  composed  of  sulphuric 
acid  and  soda.     Names  of  the  salts  are  formed  by  changing  the 
termination  of  the  name  of  tbe  acid  from  ic  into  ate,  and  from  ous 
into  lie,  and  expressing  in  full  the  name  of  the  base.     Thus,  sul- 
phuric  acid,  combined  with  bases,  forms  sulphates;  carbonic  acid, 
carbonates,  &c.,  of  the  bases  with  which  they  may  be  severally 
united;  al  sulphate  of  lime,  phosphate  of  alumina,  h^posulphate 
of  soda,  &c.     So  sulphurous  acid  forms  sulphites  ;   nitrows  acid, 
nitrites;   hyposulphurows  acid,  hyposulph/tes,  &c.,  of  the  various 
bases.  «. 

Many  of  the  metallic  oxides  serve  as  bases  of  salts,  but  in 
expressing  them  (the  salts),  the  word  oxide  is  often  omitted; 
thus,  sulphate  of  iron  is  .the  same  as  sulphate  of  the  oxide 
of  iron.  If  a  higher  oxide  than  the  protoxide  forms  the  base 
of  a  salt,  it  is  usually  expressed  in  full ;  thus,  we  have  the 
sulphate  of  the  ses^u-oxide  of  iron. 

170.  Acid  or  super  salts  are  such  as  contain  an  excess  of  acid, 
while  basic  or  sub  salts  contain  an  excess  of  base ;  salts  that  con- 
tain no  excess  of  either  acid  or  base  being  called  neutral  salts. 
A  bisulphate  contains  twice,  and  a  tersulphate  three  times  as  much, 
acid  as  a  sulphate.     Prefixes  derived  from  the  Greek  numerals 
are  often  used  to  express  the  excess  of  base  in  the  subsalts ;  as 
oYnitrate  of  lead,  a  salt  which  contains  1  equivalent  of  nitric  acid 
and  2  equivalents  of  oxide  of  lead.     The  same  thing  would  be 
expressed  by  calling  it  bibasic  nitrate  of  lead. 

The  above  explanations  will  serve  to  illustrate  the  fundamental  prin- 
ciples of  the  present  nomenclature ;  but  it  is  admitted  that  it  applies  • 
but  partially  to  the  more  complex  chemical  compounds,  which,  however, 
are  not  of  frequent  occurrence.         * 

171.  Chemical  Symbols. — Instead  of  writing  the  full  name  of 
substances,  it   is  often   convenient   to   substitute    abbreviations, 
which  are  called  the  symbols  of  these  substances.     For  a  simple 
substance,  the  first  letter  of  the  Latin  name  is  generally  used1; 
but  when  there  are  two  or  more  having  the  same  initials,  some 

QUESTIONS. — 169.  What  are  salts  ?  How  are  the  salts  named  ?  What 
is  said  of  the  names  of  salts  which  have  metallic  oxides  for  their  bases  ? 
170.  What  are  acid  or  super  salts  ?  What  basic  or  subsalts  ?  171.  What 
are  chemical  symbols  ?  How  are  they  formed  ? 


156  SYMBOLS. 

•  <* 

other  letter  of  the  name  is  connected  with  the  initial,  in  the  sym- 
bols of  all  except  one.  Thus,  0  stands  for  oxygen,  and  Os  for 
osmium;  B  for  boron,  Ba  for  barium,  and  Bi  for  bismuth;  P  for 
phosphorus,  Pd  for  palladium,  and  ft  for  platinum,  &c.  In  the 
table  on  page  145,  the  symbols  in  general  use  for  all  the  simple 
substances  are  given. 

These  symbols  indicate  single  equivalents  of  the  substances 
they  respectively  represent;  and  to  indicate  two,  threk,  or  more 
equivalents,  a  figure  is  placed  before  the  symbol,  as  the  coefficient  in 
Algebra,  or  a  little  below  it  at  the  right.  For  instance,  S  signifies 
a  single  equivalent  of  sulphur,  2  S,  3  >j,  or  S2,  S3,  &c.,  two,  three,  &c., 
eq.;  and  40,  5  0,  or  04,  C5,  four  eq.  of  oxygen,  five  eq.  of  carbon,  £c, 
To  indicate  that  several  substances  are  combined,  their  symbols 
are  simply  written  side  by  side,  as  HO,  or  with  a  comma  between 
them,  as  H,  0,  or  with  the  plus  sign  (  +  ),  as  H  +  0 ;  all  of  which 
expressions  represent  a  single  equivalent  of  protoxide  of  hydrogen, 
or  water.  The  comma  and  the  plus  sign  are  generally  made  use 
of  only  when  the  expression  is  somewhat  complex;  thus,  N05,  is 
the  symbol  for  nitric  acid,  KO  that  for  potassa,  and  KO,  N05,  or 
KO  +  N05  that  of  nitrate  of  potassa.  Sometimes  the  plus  sign 
is  used  when  the-  substances  between  which  it  is  placed  are  not 
combined,  but  only  mixed.  Generally,  in  writing  the  symbols 
of  compounds,  we  express  the  electro-positive  element  first,  as 
HO,  KO,  and  not  OH,  OK,  hydrogen  and  potassium  being  the 
positive  elements  of  these  compounds.  So  also  we  write  KO,  S03 
for  sulphate  of  potash,  and  not  S03,  KO. 

It  is  to  be  particularly  observed  that  small  figures,  placed  at 
the  right  of  letters,  apply  only  to  the  ones  to  which  they  are 
attached ;  but  large  figures,  placed  at  the  left,  like  algebraic 
coefficients,  affect  all  that  follow  them  to  the  next  comma  or 
plus  sign.  Thus,  P05  represents  phosphoric  acid ;  NaO,  soda ; 
NaO,P05,  phosphate  of  soda;  2(NaO,P05),  two  equivalents  of 
the  game  phosphate  of  soda;  but  2NaO,P05  indicates  a  single 
5q.  of  bibasic  phosphate  of  soda,  which  contains  two  eq.  of  soda> 
united  to  one  of  acid. 

In  consequence  of  the  frequent  occurrence  of  the  double  equiva- 
lent, it  is  often  expressed  by  drawing  a  line  under  the  symbol 

QUESTIONS. — How  are  compounds  expressed  by  the  use  of  these  sym- 
bols ?  How  is  a  double  atom  often  expressed  ? 


SYMBOLS.  157 

of  the  single  equivalent,  or  by  a  black  letter.  Thus,  Al  signifies 
an  eq.  of  aluminum,  and  Al  or  Al,  two  equivalents.  A103  or 
A103  is  the  symbol  for  the  sesquioxide  of  aluminum  or  alumina, 
and  means  the  same  as  A1203.  As  oxygen  forms  an  extensive 
list  of  compounds,  simple  dots  are  often  used  to  indicate  its  pre- 
sence in  them ;  the  above  symbol  for  alumina  would  then  become 
Al  — A1203, '  Other  examples  follow  the  same  rule. 

Combinations  of  these  symbols,  according  to  the  principles 
above  explained,  are  called  Chemical  Formulde ;  and  the  great 
advantages  of  their  use,  in  expressing  forcibly  complicated  chemi- 
cal changes,  will  be  fully  seea  as  we  proceed.  « 

172.  Isomerism — Polymerism. — Isomeric  compounds  (161)  are  such  as 
have  the  same  ultimate  composition,  but  differ  from  each  other  in  some 
or  all  of  their  sensible  properties.     The  term  is  derived  from  the  Greek 
isos,  equal,  and  meros,  part. 

Thus  phosphoric  acid,  P0fl,  is  known  in  three  different  conditions,  as 
ordinary,  pyro,  and  metaphosphoric  acids,  the  first  of  which  is  capable  of 
saturating  3  eq.  of  a  base,  as  soda ;  the  second,  2  eq.  of  base,  and  the 
third  only  1  eq.  In  other  properties,  also,  this  acid  in  its  different 
states  exhibits  a  diversity,  but  its  composition  in  the  different  states  is 
the  same.  There  are  other  examples  of  the  same  kind 

Polymeric  compounds  have  the  same  ultimate  composition,  but  differ 
in  their  properties ;  and  their  equivalents  are  multiples  or  sub-mul- 
tiples of  each  other.  Olefiant  gas,  C4H4,  oil  gas,  C8H8,  and  cetine, 
C3JH32,  form  a  series  of  this  kind,  having  the  same  elements  in  the  same 
atomic  proportion,  but  the  equivalent  of  the  second  being  twice  that 
of  the  first,  and  one-fourth  of  that  of  the  third.  So,  oil  of  turpentine, 
C10H8,  and  oil  of  lemons,  C20H16,  sustain  to  each  other  a  similar  relation. 
Many  other  examples  are  known. 

173.  Allotropism. — This  term  is  used  to  designate  the  different  con- 
ditions in  which  a  substance  is   sometimes  found,   as  it  regards  the 
chemical  action  of  other  bodies.     Thus,  iron,  in  its  ordinary  state,  is 
readily  dissolved  by  nitric  acid ;  but  if,  before  immersing  a  piece  of  iron 
wire  in  this  acid,  one  end  of  it  be  headed  to  redness,  or  if  it  is  connected 
with  the  positive  electrode  of  a  galvanic  battery,  or  if  it  be  immersed  in 
the  acid  in  contact  with  a  piece  of  platinum, — in  either  of  these  cases, 
the  acid  fails  to  act  upon  it.     So,  if  an  aqueous  solution  of  chlorine  be 
prepared  In  the  dark,  it  may  be  kept  in  a  dark  place  without  change  for 
a  long  time ;  but  if  the  sun  is  permitted  to  shine  upon  it  a  few  seconds, 
decomposition  will  commence,  hydrochloric  acid  will  be  formed  in  the 
water,  and  bubbles  of  oxygen  rise  to  the  surface. 

Many  other  substances  exhibit  similar  peculiarities,  and  are  said  to 
exist  in  different  allotropic  states. 

QUESTIONS. — 172.  What  are  isomeric  compounds?     What  examples  are 
given  ?    What  are  polymeric  compounds  ?     Give  an  example.     173.  What 
does  the  term  allotropism  designate  ? 
14 


CRYSTALOGRAPHY. 


CRYSTALOGRAPHY. 

174,  The  particles  of  liquid  and  gaseous  bodies,  as  they  unite 
_to  form  solids,  sometimes  cohere  together  in  an  indiscriminate 

manner,  and  give  rise  to  irregular,  shapeless  masses ;  but  more 
•frequently  they  attach  themselves  to  each  other  in  a  certain 
order,  so  as  to  constitute  solids  possessed  of  a  regularly  limited 
form.  The  process  by  which  such  a  body  is  produced  is  called 
crystalization ;'  the  solid  itself  is  termed  a  crystal;  and  the 
science,  the  object  of  which  is  to  determine  and  classify  the 
forms  of  crystals,  is  crystalograpliy. 

175.  Mode  of  producing  Crystals. — Nature  presents  us  with 
an  abundance  of  crystals  in  the  mineral  kingdom,  but  they  may 
also  be  produced  artificially  by  several  processes.     The  essential 
condition  is,  that  the  particles  of  the  substance  to  be  crystalized 
should  be  free  to  move  among  each  other,  which  is  accomplished 
by  bringing  it  into  the  liquid  state  by  solution,  or  by  melting  it. 
Alum  forms  beautiful  octahedral  crystals,  by  making  a  saturated 

solution  in  warm  water,  and  allowing  it  to  cool 
slowly.  If  a  small  tree  be  made  of  copper  wire, 
and  its  branches  immersed  in  such  a  solution  while 
cooling,  on  removing  it,  the  part  immersed  will  be 
covered  with  a  multitude  of  small  shining  octahe- 
drons, like  fruit.  If  the  solution  be  allowed  to 
stand  after  it  has  become  cold,  the  crystals  will  gradually  in- 
crease in  size  as  the  water  evaporates.  Common  salt,  blue  and 
green  vitriol,  and  many  other  substances  may  be  crystalized  in  a 
similar  manner. 

Crystalization  by  fusion  is  also  very  common.  If  a  quantity 
of  sulphur  be  melted  and  allowed  to  cool  slowly,  upon  breaking 

QUESTIONS. — 174.  Do  the  particles  of  bodies  sometimes  unite  so  as  to 
form  solids  of  a  regular  form  ?  What  are  such  solids  called  ?  175.  What 
is  the  essential  condition  for  the  formation  of  crystals  ?  What  is  the 
form  of  the  crystals  of  alum  ? 


CRYSTALOGRAPHY.  .      159 

the  crust  and  pouring  out  all  that  remains 
liquid,  a  mass'  of  crystals  will  be  found 
within,  shooting  in  every  direction,  as  repre- 
sented in  the  figure. 

The  crystalization  of  many  substances,  as 
sulphur,  corrosivAe  sublimate,  iodine,  &c.,  may 
also  be  produced  by  sublimation.  Crystalization  of  Sulphur. 

176.  Crystalization  in  Solids. — Even  in  solids,  crystalization 
sometimes  takes  place.     Copper  wire  which  has  been  long  kept  is 
said  often  to  lose  its  tenacity,  in  consequence  of  cubic  crystals  of 
the  metal  gradually  forming  in  it.     When  sugar  is  melted  and 
allowed  to  cool,  it  forms  a  hard,  transparent  mass ;  but  by  keep- 
ing some  time,  it  gradually  becomes  opaque,  and  exhibits  the 
ordinary  white  color  and  crystaline  structure   of  refined  sugar. 
Common  "lemon  candy/'  which   is  usually  sold  in   small  flat 
pieces,  an  inch  wide  and  four  inches  long,  is  beautifully  trans- 
parent when  first  formed;   but  after  a  few  hours,  crystalization 
commences  in  numerous  points,  and  gradually  extends  through 
the  mass,  which  now  becomes  opaque ;   and  at  the  same  time  its 
flavor  is  improved. 

177.  Water  of  Crystalization.  —  Many  substances,  in  crys- 
talizing,  absorb   a   large  quantity  of  water,  called   their  water 

"of  crystalization,  which  is  essential  to  the  existence  of  the 
crystals.  It  sometimes  amounts  to  half  their  weight.  When 
exposed  to  the  air,  the  water  often  evaporates,  and  the  crystals 
fall  to  powder.  They  are  then  said  to  effloresce.  Glauber's  salt 
affords  a  noted  instance  of  this. 

All  substances  are  limited  in  the  number  of  their  crystaline 
forms.  Thus,  calcareous  spar  crystalizes  in  rhbmbohedrons,  fluor 
spar  in  cubes,  and  quartz  in  six-sided,  pyramids ;  and  these  forms 
are  so  far  peculiar  to  those  substances,  that  fluor  spar  never  crys- 
talizes in  rhombohedrons  or  six-sided  pyramids,  nor  calcareous 
spar  or  quartz  in  cubes.  Crystaline  form  may,  therefore,  serve 
as  a  ground  of  distinction  between  different  substances.  But  the 
composition  of  substances  having  the  same  form  is  not  necessarily 

QUESTIONS. — How  may  sulphur  be  crystalizedv?       176.  May  crystal! 
zation  take  place  in  solids?      Give  an  example.       177.  What  is  water 
of  crystalization?     When  does  a  substance  effloresce?     Are  substances 
limited  in  the  number  of  their  crystaline  forms  ? 


160 


CRTSTALOQRAPHY. 


the  same,  nor  are  the  erystaline  forms  of  the  same  substances 
always  identical. 

178.  Primary  Forms.— The  total  number  of  erystaline  forms 
is  unlimited ;  but  it  is  found  that  all  the  more  complex  may  be 
derived  from  thirteen  of  the  more  simple  forms,  •which  are  there- 
fore called  primary  or  fundamental  forms.  These  readily  arrange 
themselves  (see  Dana's  excellent  work  on  Mineralogy^  in  six 
classes  or  systems,  which  are  characterized  by  the  comparative 
length  and  position  of  certain  imaginary  lines,  supposed  to  be 
drawn  through  them,  called  axes. 

1.  Monometric  System. — This  system  includes  the  cube,  A, 
the  regular  octahedron,  B,  and  the  rhombic  dodecahedron,  C ;  all 
of  which  have  three  equal  axes  at  riglit  angles  with  each  other. 
Hence  the  name,  from  monosj  one,  and  metron,  measure. 

The  cube,  A,  is  a  solid  with  six  equal  square  faces :    its  axes,  a,  b,  c, 


I  a 


Cube. 


All 


are  three  lines,  supposed  to  connect  the  centres  of  opposite  faces, 
its  solid  angles  are  similar,  as  also  fts  edges. 

The  regular  octahedron,  B,  is  contained  under  eight  equilateral  triangles, 


Octahedron. 


QUESTIONS.' — 178.  What  are  primary  forms?  How  many  of  these  are 
there?  In  how  many  classes  do  they  arrange  themselves?  What  are 
the  forms  of  the  monometric  system  ?  What  is  said  of  the  axes  of  the 
forms  of  this  system  ? 


C  R  Y  S  T  A  L  O  G  R  A  P  H  Y . 


161 


and  its  sixes,  a,  b,  c,  connect  opposite  solid  angles.     All  its  angles  and 
edges  are  similar. 

The  rhombic  dodecahedron,  C,  is  bounded  by  twelve  equal  rhombs;  it 
has  two  kinds  of  solid  angtes,  one  kind,  as  m,  m,  which  is  composed  of 
four  acute  plain  angles,  and  another  kind,  as  rtfn,  which  is  composed  of 


Dcdehecadron. 

three  obtuse  plain  angles.     The  axes,  #,  b,  c,  connect  the  opposite  acute 
solid  angles. 

Comparing  these  three  forms  with  each  other,  it  will  be  seen  that  the 
axes  are  the  same  in  all,  being  equal  in  length,  and  making  right  angles 
with  each  other.  .  If  any  one  of  them  is  supposed  to  be  placed  within 
another,  the  axes  of  the  two  will  entirely  correspond  throughout. 

2.  Dimetric  System. — This  system  includes  only  two  forms, 
the  square  prism,  and  the  square  octaliedron.  These  solids  have 
three  axes,  at  right  angles  to  each  other,  but  they  are  of  two 
kinds,  as  indicated  by  the  name,  from  dis,  twice,  and  metron, 
measure. 

The  square  prism,  D,  is  bounded   by  six  faces,  two  of  which,  0,  0, 


Square  Prism. 

called  the  bases,  are  squares,  but  the  four  other  faces  are  rectangles, 
the  height  of  which  may  be  either  greater  or  less  than  the  base.     The 

QUESTIONS. — AVhat  are  the  forms  of  the  dimetric  system  ?     How  are 
the  axes  of  the  forms  of  this  system  characterized  ? 
14* 


162 


CRYSTALOGRAPHY. 


axes,  a,  b,  c,  connect  the  centres  of  opposite  faces,  as  in  the  cube ; — the 
two  last  named,  b  and  c,  are  always  equal,  but  the  other,  a,  sometimes 
called  the  prismatic  axis,  is  variable,  and  may  be  either  longer  or  shorter 
than  the  others.  Its,  solid  angles  are  similar  to 
each  other,  but  the  edges  are  of  two  kinds,  the 
basal  and  the  lateral. 

The  square  octahedron,  E,  has  for  its  faces  eigh' 
equal  isosceles  triangles.  £he  axes  connect  oppo 
site  solid  angles,  and  correspond  in  every  respec'- 
with  the  axes  of  the  square  prism.  The  tw< 
therefore  properly  constitute  one  system.  In  de- 
scribing this  solid  the  variable  axis,  a,  is  always 
supposed  to  be  vertical,  the  other  two  being  hori- 
zontal. It  has  two  kinds  of  edges,  and  two  kinds 
Square  Octahedron.  of  solid  angles. 

3.  Trimeiric  System. — The  three  solids  of  this  system  are 
the  rectangular  prism,  F,  the  right  rhombic  prism,  Gr,  and  the 
rhombic  octahedron)  H.  The  name  is  from  tris,  trice,  and 
metron,  measure.  These  forms  have  three  axes  intersecting  at 
right  angles,  but  all  are  variable,  no  two  being  equal. 

The  rectangular  prism,  F,  has  six  faces,  all  of  which  are  rectangles : — 
its  three  axes,  a,  b  and  c,  connect  the  centres  of  opposite  faces,  and 
intersect  each  other  at  right  angles,  and  are  variable,  as  to  their  length. 
Its  solid  angles  are  all  similar ;  but  its  edges  are  of  three  kinds. 


Rectangular  Prism. 


Right  Rhombic  Prism. 


Rhombic  Octahedron. 


The  right  rhombic  prism,  G,  has  six  faces,  two  of  which  are  equal 
rhombs,  and  constitute  the  bases,  while  the  four  lateral  faces  are  rec- 
tangular. Its  three  axes,  a,  b  and  c,  intersect  at  right  angles,  and  are 
variable;  the  first,  a,  connecting  the  centres  of  the  bases,  but  the  other 
two,  b  and  c,  being  drawn  between  the  centres  of  opposite  lateral  edges. 
Its  solid  angles  are  of  two  kinds  and  its  edges  of  three. 

The  rhombic  octahedron,  H,  has  eight  faces,  which  are  scalene  tri- 
angles ;  its  axes,  three  in  number,  a,  b  and  c,  unite  the  apices  of  oppo- 


QPESTIONS.—  What  are  the  forms  of  the  trimetric  system? 
said  of  their  axes  ? 


What  ia 


CRYSTALOGRAPHY. 


163 


site  solid  angles,  and  in  every  respect  correspond  to  the  axes  of  the  two 
solids  last  desci-ibed.  This  solid  may  be  considered  as  composed  of  two 
pyramids  with  rhombic  bases,  united  base  to  base. 

Comparing  the  three  forms  of  this  system,  we  see  that  their  axes  are 
identical ;  comparing  the  systems  now  described  with  each  other,  we 
find  that' they  each  have  three  axes  intersecting  at  right  angles  in  the 
centre  of  the  solids ;  but  in  the  first,  or  submonometric  system,  all  are 
equal ;  in  the  second,  or  dimetric,  two  are  equal,  and  the  third  variable ; 
while  in  the  third,  or  trimetric,  all  are  variable. 

4.  Monodinic  System. — This  system  includes  two  forms,  the 
right  rhomboidal  prism,  I,  and  the  oblique  rhombic  prism,  J, 
which  have  three  axes,  a,  b  and  c,  two  of  them  making  their 
intersections  at  right  angles,  but  the  third  is  inclined.  The 
name  is  from  monos,  one,  and  clino,  to  incline.  . 

The  right  rhomboidal  prism,  I,  has  two  rhomboidal  bases,  upon  one 
of  which  in  this  figure  it  is  supposed  to  stand,  the  other  four  being 
rectangles.  The  axes  connect  the  centres  of  opposite  faces,  of  which 
a  and  b,  a  and  c,  intersect  at  right  angles,  but  b  and  c  are  inclined  to  each 
other. 


. 

'**     Q 


Right  Rhomboidal  Prism.         Oblique  Rhombic  Prism.         Right  Rhomboidal  Prism. 

The  oblique  rhombic  prism,  J,  has  its  faces  rhombs,  and  its  four  lateral 
faces  parallelograms.  Its  vertical  axis,  a,  connects  the  centres  of  the 
bases,  but  the  two  lateral  axes,  b  and  c,  are  drawn  between  the  centres 
of  the  lateral  edges.  The  last  two  intersect  at  right  angles,  and  the 
vertical  axis,  a,  makes  a  right  angle  with  b,  but  is  inclined  to  c. 

To  compare  these  two  forms,  the  right  rhomboidal  prism,  I,  must  be 
placed  upon  one  of  its  rectangular  faces,  as  in  K,  making  the  axis,  a, 
vertical ;  the  faces  m  m  and  n  n,  in  I,  will  become  respectively  m  m  and 
n  n  in  K,  and  all  the  axes  of  the  two  will  correspond.  If  now,  when  in 


QUESTION. — Comparing  now  the  axes  of  the  forms  belonging  to  the 
three  preceding  systems,  in  what  do  they  differ?  What  forms  are 
included  in  the  monoclinic  system  ?  What  is  said  of  their  axes  ? 


164 


CRYSTALOGRAPHY. 


this  position,  all  the  lateral  edges  are  removed,  as  in  E7,  we  shall  have 
the  oblique  rhombic  prism,  represented  "within  the  rhomboid.il,  as  in. 

K'  L 


A 

\=\ ----••---  -  z-y/ 


to 


Right  Rhomboitlal  Prism.  Oblique  Rhomb'l  and  Right  Rhomb'l  Prisms 

figures  Kx  and  L;   the  crystal  in  the  last  figure  being  supposed  in  the' 
same  position  as  in  I. 

5.  Triclinic  System. — A  single  form  only,  the  oblique  rhom- 

loidal  prism,  M,  belongs  to  this  system.  It 
is  bounded  by  six  faces,  but  only  those 
directly  opposite  each  other  are  equal.  Its 
basal  faces  are  rhomboids,  and  its  lateral 
edges  are  inclined  to  the  plane  of  its  base. 
Its  three  axes  are  unequal,  and  no  two  of 
them  intersect  at  right  angles.  The  name 
Oblique  Rhomboidai  Prism,  is  from  tris,  thrice,  and  clino,  to  incline. 

6.  Hexagonal  System. — This   system  includes  the  rhombohe- 
dron,  N  and  0,  and  the  hexagonal  prism,  T.     These  solids  have 


Rhoinbohedron.  Rhombohedron. 

four  axes,  one  of  which,  called  the  vertical  axis,  is  perpendicular 

QUESTIONS. — What  solid  only  belongs  to  the  triclinic  system  ?  What 
is  said  of  the  axes  of  this  form  ?  What  are  the  forms  of  the  hexagonal 
system  ?  How  many  axes  have  they,  and  how  are  they  drawn  ? 


CRYSTALOGR.APHY 


165 


to  the  other  three,  called  the  lateral  axes.     These  latter  intersect 
each  other  at  angles  of  00°,  and  are  equal. 

The  rhombohedron  is  of  two  kinds,  the  obtuse,  N,  and  the  acute,  0 ; 
in  each  all  the  six  faces  are  equal  rhombs,  and  in  each  there  are  two 
e^lid  angles,  diagonally  opposite,  which  are  formed  by  three  equal  plain 
%ugles.  Between  these,  one  axis,  a,  is  drawn,  called  the  vertical  axis ; 
vad  in  describing  the  solid  this  is  always  supposed  to  be  in  a  vertical 


Ehombohedron. 

position.     The  other  three  axes,  b,  c  and  d,  unite  the  centres  of  opposite 
lateral  edges. 

Of  the  twelve  edges,  six  (three  above  and  three  below)  are  connected 
with  the  extremities  of  the  vertical  axis  around  which  they  are  sym- 
metrically placed.  The  other  six,  called  the  lateral  edges,  are  also 
situated  around  this  axis  symmetrically,  and  at  equal  distances  from  it. 
This  is  readily  seen  by  looking  downward  upon  a  crystal  of  this  form 
when  in  position,  a  section  through  the  centre  perpendicular  to  the 
vertical  axis  being  plainly  a  regular  hexagon,  as  in  the  figure  P. 


Section  Rhombohedron 


Secondaries. 


By  replacing  the  six  lateral  edges  by  planes  parallel  to  the  vertical 
axis,  a,  a  hexagonal  prism,  terminated  by  three-sided  pyramids,  is  pro- 
duced, represented  in  R.  Removing  in  a  similar  manner  the  lateral 
solid  angles,  we  have  the  form,  S,  which  is  essentially  the  same  as  the 

QUESTIONS. — How  is  the  hexagonal  prism  terminated  with  three-sided 
pyramids  produced  from  the  rhombohedron  ? 


166 


CRYSTALOGRAPHY. 


last  except  the  terminal  pyramids ;  and  by  a  removal  of  the  terminal 

pyramids  a  regular  hexagonal  prism,  T, 
will  be  found. 

In  a  similar  manner,  the  rhombo- 
hedron  may  be  derived  from  the  hex- 
agonal prism,  by  a  replacement  of  the 
alternate  basal  edges  of  the  prism  -, 
first  in  the  form  represented  in  U ; 
and  the  replacement  being  continued 
until  the  faces  of  the  original  prism 
are  obliterated,  the  resulting  solid  will 
Hexagonal  Prism.  be  the  rhombohedron. 

179,  Secondary  Forms, — Secondary  forms  are  derived  from 
the   primary,    by  regular,    systematic  changes   or  modifications 
upon  the  angles  or  edges.     Their  number  is  unlimited. 

A  general  discussion  of  the  laws  of  these  modifications  cannot  be  here 
introduced,  and  only  a  few  further  illustrations.  The  connection  between 
the  different  forms  of  each  of  the  six  systems,  it  is  believed,  has  been 
made  plain ;  and  also  the  modifications  by  which  one  form  is  evolved 
from  another,  as  the  oblique  rhombic  prism,  J,  from  the  right  rhom^ 
boidal,  I,  in  the  monoclinic  system. 

By  the  same  process  the  secondary  forms  are  obtained  from  the  pri- 
maries ;  indeed,  in  each  system  containing  more  than  one  form,  any  one 
in  that  system  may  be  taken  as  the  primary,  of  which  the  others  are  then  to 
be  considered  as  secondaries.  Thus,  in  the  dimetric  system,  either  the 
square  prism,  or  the  square  octahedron  may  be  taken  as  the  primary  form, 
from  which  the  other  may  be  derived  in  the, manner  pointed  out.  There- 
fore, although  it  is  customary  to  consider  as  primary  all  the  thirteen  forms 
mentioned  above  as  belonging  to  the  several  systems,  yet  the  whole  num- 
ber necessary  for  the  derivation  of  all  known  forms  is  only  six,  one  for 
each  of  the  six  systems. 

180.  Laws  of  Modification  of  Forms/ — The  modification  of 
the  forms  of  crystals  always  takes  place  in  accordance  with  cer- 
tain laws,  which  may  be  stated  as  follows,  viz  :     All  the  similar 
parts  of  the  crystal  will  be  similarly  and  simultaneously  modi- 
jied)  or  half  of  the  similar  parts  will  be  similarly  modified, 
independently  of  the  other  half. 

In  the  forms  of  the  monometric  system  all  the  parts  are  similar,  and 
all  will  therefore  be  modified  in  the  same  manner;  but  this  is  not  the 


QUESTIONS. — How  may  the  rhombohedron  be  produced  from  the  hex- 
agonal prism?  179.  What  are  secondary  forms  ?  In  each  of  the  above 
systems  may  all  the  forms  be  derived  from  one  ?  How  many  funda- 
mental forms  only  are  then  necessary  ?  180.  Do  the  modifications  in 
the  forms  of  crystals  always  take  place  according  to  fixed  laws?  What 
is  the  general  law  stated  ?  Are  all  the  parts  similar  in  the  forms  of  the 
monometric  system  ? 


CRTS  HA  LOGRAPHY, 


167 


case  with  the  forms  of  the  other  systems.  In  the  dimetric  system,  for 
instance,  the  square  prism,  D,  (page  161,)  has  two  kinds  of  faces,  the 
basal  and  the  lateral,  and  also  two  kinds  of  edges,  but  only  one  kind 
of  solid  angles. 

The  lateral  edges,  being  formed  by  the  meeting  of  similar  faces,  may 
be  truncated,  that  is,  replaced  by  a  plane  equally  inclined  to  the  two 
faces ;  but  the  basal  edges,  being  formed  by  the  meeting  of  dissimilar 
faces,  do  not  admit  of  truncation.  The  new  plane  replacing  one  of  these 
edges  will  always  be  more  inclined  to  one  of  the  old  faces  than  to  the 
other. 

The  solid  angles  are  all  alike,  but  each  being  formed  by  two  plane 
angles  that  are  similar  to  each  other,  but  unlike  the  third,  they  cannot 
be  truncated.  The  figure  V  represents  a  square  prism  with  its  lateral 


W 


Replacements. 


edges  truncated,  and  in  W,  we  see  one  of  the  same  with  its  basal  edges 
replaced,' but  each  of  the  new  planes  is  unequally  inclined  to  the  adja- 
cent basal  faces  0,  and  lateral  faces  I.  In  the  figure  X,  the  square 
prism  has  its  angles  replaced,  the  new  plane,  p,  making  equal  angles 
with  the  faces  I,  but  not  with  0. 

By  continuing  the  replacements  seen  in  W,  or  in  X,  until  the  old  faces 
are  entirely  obliterated,  it  is  evident  that  we  shall  have  the  square  octa- 


Square  Octahedron. 

hedron,  Y,  which  sustains  the  same  relation  to  the  square  prism  as  the 
regular  octahedron  does  to  the  cube. 

QUESTIONS. — What  is  said  of  the  faces  of  the  square  prism?  What  is 
said  of  the  faces  forming  the  basal  edges?  Can  these  edges  then  be 
truncated  ?  May  the  lateral  edges  be  truncated  ?  If  we  replace  the 
basal  edges  on  the  angles  of  the  square  prism,  continuing  the  replace- 
ment until  the  original  faces  are  all  obliterated,  what  form  will  result  ? 


168  0  R  Y  S  T  A  L  O  G  II  A  P  II  Y . 

* 

By  examining  the  forms  belonging  to  other  systems,  and  applying  the 
game  general  law,  it  becomes  apparent  that  the  variety  of  forms  capable 
of  being  produced  is  really  unlimited,  but  the  subject  cannot  be  pursued 
further  in  this  place. 

181.  Formation  of  Crystals. — When  a  substance  crystalizes  in  circum 
stances  to  admit  of  observation,  a  very  small  crystal  is  first  seen,  which 
gradually  increases  in  size  by  the  deposition  of  particles  on  the  different 
faces.  If  this  addition  of  matter  be  equal  on  all  the  faces  the  form  is 
continued  the  same,  but  if  there  is  more  added  on  some  of  the  faces  than 
on  others  the  crystal  becomes  more  or  less  irregular.  Changes  of  form, 
in  accordance  with  the  laws  above  mentioned,  we  may  suppose  to  be  pro- 
duced in  the  following  manner.  Let  us  suppose  a  substance  crystalizing 
in  the  monometric  system,  as  galena,  or  common  salt.  A  cube  is  formed 
and  is  gradually  increasing  in  size  by  equal  additions  upon  every  face, 
but  at  length,  from  some  cause  not  understood,  a  change  takes  place,  and 
regular  spaces  are  left  at  the  angles  or  edges  of  the  cube.  We  will  sup- 
pose that  at  each  edge  of  the  cube  there  is  left  a  deficiency,  or  decrement, 
of  one  row  of  particles  for  every  addition  upon  the  surface;  this  will 
occasion  the  formation  of  planes  upon  the  edges,  and.  if  continued,  will 
result  in  the  production  of  a  rhombic  dodecahedron. 

Or  let  us  suppose,  as  the  additions  are  made,  a  decrement  occurs  at 
the  angles  only  .-—this  will  result  in  the  replacement  of  the  angles.  Let 
A  be  a  small  cube  on  which  deposits  are  taking  place,  as  suggested 
above,  leaving  decrements  at  the  angles.  After  a.  time  it  will  have  the 
form  B,  and  by  a  continuation  of  the  process  will  become  of  the  form  C, 
and  then  of  D  ;  but  unlike  the  forms  represented  in  the  figures,  it  will 
be  constantly  increasing  in  size.  But  the  form,  D,  is  evidently  that  of  a 


Monometric  Forms. 

regular  octahedron  with  all  its  solid  angles  replaced  by  planes ;  and  we 
suppose  the  process  continued  until  the  perfect  octahedron  would  be 
formed.  By  reversing  this  process,  commencing  with  the  regular  octa- 
hedron, and  supposing  additions  to  be  made  on  the  faces,  with  decre- 
ments at  the  angles,  and  continuing  the  process  sufficiently,  the  cube 
will  eventually  be  produced. 

Whether  this  is  the  real  mode  by  which  the  variously  modified  second- 
ary forms  are  produced,  we  may  never  be  able  to  determine  fully ;  but, 
in  the  absence  of  positive  proof,  this  has  been  presented  as  theoretically 
possible. 

QUESTIONS. — 181.  Ho'w  do  crystals  increase  in  size  ?  Illustrate  the  mode 
in  which  a  secondary  form  may  be  produced  in  the  crystalization  of  com- 
mon salt  by  a  supposed  decrement  upon  the  edges  ? 


OEYSTALOGBAPHY.  169 

182.  Cleavage. — Crystals  are  generally  capable  of  separation 
in   certain  directions   by  natural  joints; — a   property  which  is 
denominated  cleavage.     In  the  primary  forms  this  usually  takes 
place  in  planes  parallel  to  the  faces,  but  may  also  occur  in  planes 
paraLel  to  any  of  the  faces  of  secondary  forms  belonging  to  the 
species.     It  will  usually  be  found  in  crystals  that  cleavage  is  much 
m'>re  easy  in  some  directions  than  in  others;  and  the  general  rule 
is  that  it  will  take  place  with  equal  facility  parallel  to  similar 
faces,  and  only  in  this  direction. 

183.  Isomorphism. — Isomorphous  substances  (from  isos,  equal, 
and  morphe,  form),  strictly  are  substances  which  crystalize  in  the 
same  form ;    but  the   term  is-  generally  used   to  indicate   those 
bodies   which,   in    the    compounds   they  form,    are    capable  •  of 
replacing  each  other,  without  changing  the  forms  of  the  crystals 
of  these  compounds.     Thus  magnesia  and  lime,  and  the  protoxides 
of  iron  and  manganese,  form  a  group,  any  one  of  which  may  replace 
another  in  whole  or  in  part  in  the  compounds  they  form.     So  also 
alumina  (sesquioxide  of  aluminum),  and  sesquioxide  of  iron,  form 
another  group,  and  phosphoric  and  arsenic  acids  another. 

In  general,  isomorphous  substances  will  be  found  to  possess 
other  analogous  properties;  and  the  compounds  they  form  will 
often  closely  resemble  each  other  in  all  their  leading  properties. 
We  have  an  excellent  illustration  of  this  in  the  alums,  of  which 
there  are  several,  but  all  possessing  the  same  crystaline  form, 
and  the'  same  astringent,  sweetish  taste,  the  same  solubility  in 
water,  &c.  Below  are  the  formula  representing  their  composition 

Common  alum KO,S03  +  AJ203,  3  S03  +  24  HO. 

Iron  alum KO,S03  +  Fe203,  3  S03  +  24  HO. 

Chromium  alum KO,S03  +  Cr203,  3  S03  +  24  HO. 

Soda  aHim .NaO,S03-f  A1203,  3  S03  +  24  HO. 

Ammonia  alum NH40,S03  +  A1203,  3  S03  +  24  HO. 

QUESTION, — 182.  What  is  meant  by  cleavage  ?  How  does  this  usually 
take  place  in  primary  forms  ?  Is  cleavage  made  with  equal  facility  in 
all  directions?  183.  What  are  isomorphous  substances?  Will  isomor- 
phous substances  usually  be  found  to  possess  other  analogous  properties 
besides  those  of  form  ?  What  is  said  of  the  alums  iu  this  connection  ? 
15 


170  CRYSTALOGRAPHY. 

Comparing  these  formulae,  one  after  another,  with  the  first, 
that  of  common  alum,  we  perceive  that  in  iron  and  chromium 
alums  the  sesquioxide  of  aluminum  is  replaced  by  the  sesquioxides 
of  iron  and  chromium  respectively;  and  in  the  soda  and  ammonia 
alums,  the  potash  is  replaced  in  one  by  soda  and  in  the  other  by 
ammonia  (oxide  of  ammonium).  These  several  sesquioxides  are 
therefore  isomorphous,  as  are  also  the  potash,  soda,  and  oxide  of 
ammonium  which  replace  each  other  in  the  other  formula.  This 
list  of  alums  might  be  still  further  extended ;  and  all  constitute  a 
single  family  of  compounds  formed  on  the  same  type  and  possess- 
ing very  similar  properties. 

Many  other  similar  groups  of  compounds  might  be  given  in 
which  isomorphous  substances  replace  each  other,  but  the  above 
will  suffice. 

The  following  group  of  simple  substances  that  are  isomorphous,  is  from 
Gmelin. 

1.  Carbon,  phosphorus,  potassium,  titanium,  bismuth,  cadmium,  lead, 
iron,  copper,  silver,  and.  gold. 

2.  Potassium,  sodium,  lithium,  calcium,  zinc,  lead,  and  silver.    . 

3.  Oxygen,  sulphur,  and  chlorine. 

4.  Arsenic,  antimony,  and  tellurium. 

5.  Platinum,  iridium,  and  osmium. 

184.  Dimorphism, — Dimorphous  substances  (c??!s,  double,  and 
morphe,  form,)  are  such  as  are  capable  of  crystalizing  in  two 
forms  belonging  to  different  systems  of  crystalization.  A  few 
substances  are  known  which,  under  different  circumstances,,  crys- 
talize  in  three  forms,  and  are  therefore  called  trimorphous. 

Among  the  simple  substances,  carbon,  sulphur,  and  perhaps 
copper,  are  .  dimorphous.  Carbon,  as  diamond,  takes  a  form 
belonging  to  the  monometric  system,  but,  as  graphite,  it  is  found 
in  the  hexagonal  system.  It  is  scarcely  necessary  to  remark  that 
in  these  different  forms  many  of  its  properties  are  essentially  dif- 
ferent. As  diamond,  it  is  the  hardest  substance  known,  and  is 
transparent,  but,  as  graphite,  it  is  comparatively  soft,  perfectly 
black,  and  opake. 

Sulphur  when  crystalized  by  melting  and  slow  cooling  (175) 

QUESTIONS. — How  do  the  formula  for  the  different  alums  compare 
with  each  other?  184.  What  are  dimorphous  substances?  What 
simple  substances  are  mentioned  as  being  dimorphous  ? 


CRYSTALOGRAPIIY.  171 

the  crystals  take  forms  belonging  to  the  monoclinic  system,  but 
the  native  crystals,  and  those  obtained  by  dissolving  sulphur  in 
the  bisulphide  of  carbon,  belong  to  the  trimetric  system. 

Many  compound  bodies  are  found  to  crystalize  in  two  or  more  forms ; 
and  sometimes  it  has  been  ascertained  that  the  particular  form  produced 
•will  depend  in  some  degree  upon  the  temperature  of  the-crystalizing  solu- 
tion. Carbonate  of  lime  usually  crystalizes  in  forms  of  the  hexagonal 
system,  but  occasionally  it  forms  crystals  of  the  trimetric  system,  and  is 
then  called  arragonite.  Such  researches' as  have  been  made  on  the  sub- 
ject indicate  that  it  takes  the  form  last  mentioned  when  crystalizing  at 
about  212°,  but  forms  crystals  of  the  hexagonal  system  only  at  very  low 
or  very  high  temperatures. 

In  some  cases  a  change  of  the  crystaline  arrangement  of  the  particles 
of  a  body,  attended  by  a  change  of  color,  is  produced  by  a  mere  varia- 
tion of  temperature.  Thus  protiodide  of  mercury  sublimed  at  a  very 
gentle  heat  forms  small  dimetric  crystals  of  a  scarlet  color,  but  if  sub- 
limed at  high  temperatures  the  crystals  are  monoclinic  and  of  a  sulphur 
yellow  color.  The  scarlet  crystals  become  yellow  by  being  heated,  but 
turn  red  again  when  cooled. 

The  yellow  crystals  obtained  by  sublimation  retain  this  color  when 
cooled,  but  if  scratched  or  disturbed  by  some  pointed  instrument,  they 
at  once  turn  red  at  the  point  touched,  and  the  change  of  color  soon 
extends  to  the  whole  mass  of  crystals  in  contact. 

QUESTIONS. — Upon  what  has  the  form  of  dimorphous  substances  some' 
times  been  found  to  depend  ? 


PART   III. 

SPECIAL    CHEMISTRY  — INORGANIC. 

185,  Classification  of  Elements. — Having  discussed  under  the 
head  of  GENERAL  CHEMISTRY  the  important  principles  pertaining 
to  chemical  changes  generally,  we  are  now  prepared  for  the  exami- 
nation of  the  various  Simple  substances,  or  elements,  found  in  nature, 
and  their  inorganic  compounds  so  far  as  may  cowe  within  the  objects 
of  the  present  work.  And,  in  accordance  with  general  usage,  we 
shall  divide  them  into  the  two  great  classes  of  non-metallic  and 
metallic  elements,  called  also  metalloids  and  metals. 

Though  this  division  is  universally  recognized  by  writers  upon 
this  science,  yet  it  is  founded  upon  properties  which  are  not  abso- 
lute, and  are  much  more  distinctly  seen  in  some  of  the  elements 
than  in  others;  a  degree  of  vagueness  therefore  attaches  to  it, 
and  several  of  the  simple  substances  are  not  readily  determined, 
being  referred  to  either  of  the  divisions  with  nearly  equal  pro- 
priety. It  is  however  retained'  because  of  its  convenience ;  and, 
following  the  example  of  Regnault,  we  shall  consider  as  non-me- 
tallic the  following  fifteen  elements,  which  are  further  arranged 
in  natural  groups.  Of  these,  silicon,  tellurium,  and  arsenic  have 
not  unfrequently  been  classed  with  the  metals  which  they — and 
especially  the  last  two — strikingly  resemble  in  some  of  their  pro- 
perties. Iodine  and  bromine  also,  though  with  less  reason,  have 
been  sometimes  regarded  as  metals. 

All  the  elements  may  enter  into  the  composition  of  inorganic 
compounds,  which  are  produced  in  the  mineral  world,  and  may 
be  formed  artificially  j  but  only  a  few  of  them — more  especially 
carbon,  hydrogen,  oxygen,  and  nitrogen — form  organic  compounds, 
which  originate  almost  exclusively  in  plants  and  animals. 

QUESTIONS. — 185.  Into  what  two  classes  are  the  elementary  substances 
divided  ?  How  many  non-metallic  elements  are  there  ?  May  al)  the 
elements  enter  into  the  composition  of  inorganic  or  mineral  compounds? 
What  four  are  mentioned  as  forming  most  organic  compounds  ? 

(172) 


NON-METAL  LIC    ELEMENTS.  173 

A  further  discussion  of  the  relations  of  organic  and  inorganic 
bodies  will  be  introduced  hereafter. 

186.  For  the  sake  of  convenience  we  shall  arrange  the  non- 
metallic  elements  in  the  five  following  groups,  and  introduce  them 
for  description  in  the  order  in  which  their  names  appear.  Among 
the  individuals  of  some  of  the  groups  a  striking  resemblance -is 
manifest,  but  in  other  groups  this  is  less  apparent. 

Each  element  will  first  be  described,  apd  afterwards  will  be 
introduced  the  more  important  compounds  it  forms  with  the 
other  elements  previously  described. 


METALLOIDS,    OR   NON-METALLIC   ELEMENTS. 


GROUP.  I.     OXYGEN.     HYDROGEN.     NITROGEN. 

These  substances  are  brought  together  in  the  same  group  merely  for 
the  sake  of  convenience ;  each  one  properly  constitutes  a  class  by  itself. 

The  first,  oxygen,  is  more  abundant  than  any  other  element,  constitu- 
ting from  30  to  50  per  cent,  of  the  whole  globe,  or  at  least  that  part  of  it 
accessible  to  man.  It  forms  compounds  with  nearly  all  other  elements. 

Hydrogen  is  a  highly  electro-positive  substance,  and  in  some  of  its 
properties  resembles  the  metals. 

Nitrogen  is  noted  for  its  very  feeble  affinity  for  the  other  elements, 
•whether  electro-positive  or  electro-negative.  It  has  sometimes  been 
classed  with  phosphorus  and  arsenic,  to  which  it  has  some  resemblance. 

GROUP  II.     CHLORINE.     IODINE.     BROMINE.     FLUORINE. 

These  electro-negative  elements  constitute  a  very  distinct  natural 
family :  each  forms  a  single  acid  compound  with  hydrogen,  and  all 
except  the  last  form  analogous  acid  compounds  with  oxygen. 

GROUP  III.     SULPHUR.     SELENIUM.     TELLURIUM. 

These  elements,  especially  the  first  two,  closely  resemble  each  other; 
they  also  form  acid  compounds  both  with  oxygen  and  hydrogen,  which 
Are  analogous  in  their  constitution. 

QUESTIONS. — 186.  In  how  many  groups  are  the  metalloids  arranged? 
N.°me  the  elements  of  the  first  group.  Why  are  these  arranged  together? 
Name  those  of  the  second  group.  Name  the  elements  of  the  third  group 

15* 


174  OXYGEN. 

GROUP  IV.     PHOSPHORUS,     ARSENIC. 

Two  elements  very  similar  in  many  of  their  properties,  and  forming 
similar  compounds  with  oxygen  and  hydrogen.  Many  of  their  com- 
pounds are  isomorphous.  Antimony  also  properly  belongs  to  the  group. 

GROUP  V.     CARBON.     SILICON.     BORON. 

Combustible  bodies  incapable  of  being  volatilized  even  at  the  highest 
temperatures  known,  and  forming  feeble  acids  with  oxygen. 


GROUP  I. 

OXYGEN  "|  Gaseous  at  all  temperatures  ;  but  having  few  other  points 
HYDROGEN  )•  of  resemblance.  A  compound  of  the  first  two  constitutes 
NITROGEN  J  water, — a  mixture  of  the  first  and  last,  atmospheric  air. 


OXYGEN. 

Symbol,  0;  Equivalent,  8  ',  Density,  1-106. 

187.  History.  —  Oxygen  (from  oxus,  acid,  and  gennao,  to  pro- 
duce) was  discovered  by  Priestly  and  Scheele,  independently  of 
each  other,  in  1774.     It  has  been  called  empyreal  air,  because 
it    supports   combustion,    and   vital  air,    because   necessary   to 
respiration.      It  is  the   most  abundant  of  the  elementary  sub- 
stances, and  constitutes  from  30  to  50  per  cent  of  the  mass  of  the 
globe,  or  at  least  that  part  of  it  accessible  to  man  ;  it  forms  also 
an  ingredient  of  nearly  all  animal  and  vegetable  compounds. 

188.  Preparation.  —  Oxygen  is  a  gaseous  substance,  and  may 
be  obtained  from  several  sources;  but  the  best  method  to  procure 
it,  when  only  a  small  quantity  is  required,  is  to  heat  an  ounce  or 
less  of  chlorate  of  potash  in  a  green  glass  flask  or  retort.     This 
salt  is  composed  of  chloric  acid,  C105,  and  potash,  KO;    and, 
when  heated  nearly  to  redness,  gives  up  the  whole  of  its  oxygen, 
as  shown  by  the  following  formula.     Thus, 


each  atom  of  the  salt  yielding  one  atom  of  chloride  of  potassium, 
and  six  atoms  of  oxygen.     The  process  succeeds  better  if,  before 

QUESTIONS.  —  Name   the    elements   of    the   fourth    and    fifth   groups. 

187.  What  important  facts  are   mentioned  in   the  history   of  oxygen? 

188.  Describe  the  mode  of  preparing  oxygen  from  chlorate  of  potash? 
How  is  it  to  be  collected? 


OXYGEN. 


175 


heating,  the  salt  is  intimately  mixed  with  an  equal  weight  of  pow- 
dered peroxide  of  manganese,  or  oxide  ;>f  copper. 

The  accompanying  .  figure 
will  .serve  to  illustrate  the. 
arrangement  of  the  apparatus 
required  for  the  experiment. 
The  salt,  contained  in  a  retort, 
is  heated  by  a  spirit-lamp, 


which  produces  no  smoke,  and  reparation  of  Oxygeu. 

the   gas,   as   it   forms,  passes 

under  a  receiver  filled  with  water,  and  placed  on  a  shelf  in  a 
pneumatic  cistern,  a  section  of  which  is  shown  in  the  figure. 
The  receiver  is  open  at  the  bottom,  and  it  is  first  filled  with 
water  by  plunging  it  in  the  cistern,  and  then  bringing  it  to  its 
upright  position,  and  raising  it  carefully  to  its  place  upon  the 
shelf,  which  is  just  beneath  the  surface  of  the  water.  The  water 
rises  in  the  receiver,  in  consequence  of  the  atmospheric  pressure 
(see  the  author's  Natural  Philosophy,  p.  135) ;  and  when  the 
gas  is  forced  underneath  it,  it  rises  in  bubbles,  displacing  the 
water,  and  occupying  the  highest  part  of  the  receiver, — the  shelf 
being  supposed  to  have  an  aperture  in  it,  to  allow  the  gas  to  pass 
upward,  and  the  water  also  to  escape. 

189.  We  have  in  the  above  equation  the  first  instance  that 
occurs  in  this  work  of  the  use  made  of  symbols  to  illustrate 
chemical  changes.  The  expression  constitutes  a  proper  equation, 
but  it  has  peculiar  properties,  in  which  it  differs  from  algebraic 
equations.  The  separate  symbols  in  the  equation,  of  course, 
indicate  equivalents  or  atoms  of  the  elements  symbolized,  and  the 
manner  in  which  they  are  combined  in  the  first  member  is  also 
designed  to  indicate  the  mode  of  combination  of  the  several  sub- 
stances expressed,  before  any  change  is  produced;  while  the 
second  member  of  the  equation  shows  the  state  or  mode  of  combi- 
nation of  the  same  elements  after  the  change  has  been  produced. 
There  must  therefore  be  found  represented  in  each  member 
of  the  equation  the  same  elements  (and  no  others),  and  the  same 

QUESTIONS. — 189.  What  is  the  design  of  the  equation  in  the  preceding 
paragraph  ?  What  is  expressed  in  the  first  member  of  the  equation  ? 
What  in  the  second  ?  What  is  required  in  the  two  members  in  equations 
of  this  kind  ?  . 


176  OXYGEN. 

member  of  atoujs  of  eaoh  element.  Thus,  in  the  above  equation 
we  have  represented  in  each  number  1  eq.  of  potassium,  1  eq.  of 
chlorine,  and  6  eq.  of  oxygen.  Of  course,  if  the  sum  of  these 
were  represented  in  numbers,  it  would  be  the  same  for  each 
member.  These  remarks  apply  in  all  similar  cases. 

Whj?n  a  large  quantity  of  oxygen  is  to  be  obtained,  it  is  more 
economical  to  make  use  of  saltpetre  (nitrate  of  potash) ;  but  a 
much  greater  heat  is  required  to  decompose  it,  and  an  iron  retort 
must  therefore  be  substituted,  instead  of  glass.  The  iron  retort 
containing  the  saltpetre  is  placed  in  a  furnace,  the  heat  of  which 
ean  be  easily  regulated,  and  a  lead  tube  is  connected  with  it, 
leading  to  the  pneumatic  cistern.  As  soon  as  'the  bottle  has 
attained  a  full  red-heat,  the  gas  begins  to  come  over;  and  if  care 
is  taken  to  prevent  the  heat  becoming  too  great,  very  pure 
oxygen  will  be  obtained.  The  changes  that  take  place  are  illus- 
trated by  the  following  formula : 

KO,N05=nKO,N03  +  20. 

Thus,  each  atom  of  nitrate  of  potash  yields  one  atom  of  hyponi- 
trite  of  potash,  and  two  atoms  of  oxygen. 

This  gas  may  also  be  procured  from  the  peroxides  of  man- 
ganese, lead,  and  mercury,  and  from  other  substances.  A  ready 
method  to  procure  it  from  the  peroxide  of  manganese  is  as  fol- 
lows: Let  a  flask  of  green  glass  be  partly  filled  with  the  per- 
oxide, and  then  enough  strong  oil  of  vitriol  poured  upon  it  to 
moisten  it  thoroughly,  and  then  apply  the  heat  of  an  alcohol 
lamp.  By  this  process  sulphate  of  protoxide  of  manganese  is 
formed,  and  oxygen  gas,  as  shown  by  the  following  equation  : 

Mn  02  -f  S03  =  MnO,  S03  +  0 

It  is  thus  seen  that  every  atom  of  the  oxide  of  manganese  will 
yield  one  atom  of  oxygen.  To  insure  purity  it  is  well  to  pass  the 
gas  as  it  is  formed  through  a  weak  solution  of  potassa  by  means 
of  a  three-necked  bottle,  as  shown  in  the  figure  on  next  page. 

QUESTIONS. — May  oxygen  be  prepared  from  nitrate  of  potash  ?  De- 
scribe the  mode  of  preparing  it  by  the  use  of  peroxide  of  manganese  and 
sulphuric  acid. 


OXYGEN. 


177 


Preparation  of  Oxygen. 

"Whatever  mode  of  preparing  it  may  be  adopted,  the  first  por- 
tions of  gas  that  come  over  should  always  be  allowed  to  escape, 
as  it  will  be  mixed  with  atmospheric  air,  contained  in  the  appa- 
ratus at  the  beginning  of  the  operation. 

190.  It  is  always  easy  to  calculate  the  quantity  of  oxygen 
which  any  given  quantity  of  materials  we  may  desire  to  use  will 
afford. 

We  will  suppose  that  1  oz.  of  chlorate  of  potash  is  to  be  employed, — 
how  many  cubic  inches  of  oxygen  will  it  afford  ? 

There  are  in  each  equivalent  of  the  chlorate  of  potash  1  eq.  of  potash 
and  1  eq.  of  chloric  acid,  composed  as  follows,  viz  : 


KO  =47-1 


=  122-5 


of  which  48  parts,  or  6  eq.,  are  oxygen.  We  have  then  the  following 
proportion : 

122-5  :  48  :  :  480  :  z, 

whence  x  ==  188  grs.  for  the  weight  of  the  oxygen  in  1  oz.  of  the  chlorate. 
Now  100  cubic  inches  of  oxygen  (192)  weigh  34-28  grains^  aud  we  have 
therefore  this  proportion : 

34-28  :  100  :  :  188  :  z, 
or  x  =  548  cubic  inches,  or  about  2£  gallons. 


QUESTION. — 190.  Supposing  the  chlorate  of  potash  used  to  prepare  frhe 
gas,  how  may  we  calculate  the  quantity  that  may  be  produced  from  an 
ouilce  of  the  salt  ? 


178 


OXYGEN. 


191.  Oxygen  gas  is  also  given  off  by  plants 
under  the  influence  of  light.  Let  a  sprig  of 
mint  be  placed  in  a  white  glass  globe,  which  ia 
then  to  be  filled  quite  full  of  spring-water,  and 
the  mouth  inverted  in  a  tumbler  of  water,  as 
shown  in  the  figure.  It  is  then  to  be  placed  in 
the  direct  rays  of  the  sun  ;  and  in  a  short  time, 
bubbles  of  gas  will  be  seen  collecting  in  the  upper 
Oxygen  from  Plants,  part  of  the  glass,  which  is  nearly  pure  oxygen. 

192.  Properties. — Pure  oxygen  is  a  colorless  gas,  without  odor 
or  taste,  and  has  never  yet  been  reduced  to  the  liquid  state  by 
any  degree  of  cold  or  pressure.  It  is  very  slightly  absorbed  by 
water,  100  cubic  inches  of  that  liquid  taking  up  3  or  4  of  the  gas. 
It  is  heavier  than  air,  1 00  cubic  inches  weighing  34  28  grains,  while 
the  same  volume  of  air  weighs  only  31  grains,  the  temperature  be- 
ing at  60°  F.,  and  the  barometric  pressure  at  30  inches.  Its  density 
is  therefore  1-106.  It  has  a  very  extensive  range  of  affinity,  enter- 
ing into  combination  with  all  the  other  elements  except  fluorine. 

Oxygen  is  a  powerful  supporter  of  combustion;   and  all  sub- 
stances that  are  capable  of  burning  in  the  open  air,  burn  in  it 
with  far  greater  brilliancy.     A  piece  of  wood,  on  which  the  least 
spark  of  light  is  visible,  bursts  into  flame  the  moment  it  is  put 
into  a  jar  of  oxygen  ;  a  recently  extinguished 
candle,  with  the  least  spark  of  fire  upon  the 
wick,   is  relighted ;    lighted    charcoal   emits 
beautiful  scintillations;  and  phosphorus  burns 
with  so  powerful  and  dazzling  a  light  that 
the  eye  cannot  bear  its  impression.     Even 
iron  and  steel,  which  are  not  commonly  ranked 
among  the  inflammables,  undergo  rapid  com- 
bustion in  oxygen  gas. 

The  combustion  of  iron  and  steel  is  effected 
by  introducing  it  in  the  form  of  wire  or' thin 
slips, — as    pieces    of  watch-spring,  —  into  a 
Combustion  of  iron.       vessel  of  the  gas,  as  shown  in  the  figure.    The 

QUESTIONS. — 191.  How  may  it  be  shown  that  plants  evolve  oxygen 
under  the  influence  of  light?  192.  What  are  some  of  the  properties 
of  oxygen  ?  '  Why  is  it  called  a  supporter  of  combustion  ?  Why  is  a 
candlo  recently  extinguished  relighted  when  plunged  in  the  gas? 


OXYQ.EN. 


179 


combustion  is  commenced  by  attaching  to  the  lower  extremity  a 
piece"  of  sp  ink  or  other  combustible,  which  is  ignited  the  moment 
it  is  to  be  introduced  into  the  gas.  As  the  combustion  progresses, 
if  the  cork  is  tight,  the  water  contained  around  the  bottom  of  the 
receiver  in  the  shallow  dish  is  seen  to  rise,  and  more  must  be 
poured  in,  to  prevent  the  entrance  of  air  from  without.  This  is 
occasioned  by  the  absorption  of  the  oxygen  by  the  iron,  to  form 
oxide  of  iron,  which  falls  in  melted  globules  into  the  dish.  When 
a  lighted  candle  is  let  down  by  a  wire  into  a 
jar  of  this  gas,  as  in  the  figure,  the  case  is 
different ;  the  candle  burns  for  a  time  with  in- 
creased splendor,  but  soon  the  flame  begins  to 
diminish,  and  at  length  entirely  disappears, 
without  any  diminution  of  the  volume  of  gas 
contained  within.  If  the  candle  be  relighted 
and  returned  to  the  receiver,  it  is  now  instantly 
extinguished,  the  gas  having  lost  entirely  its 
power  of  supporting  combustion.  The  reason 
is,  that  the  oxygen  has  disappeared,  and  a  new 
gas,  carbonic  acid,  C02,  taken  its  place,  which  Taper  in  Oxysen< 
has  exactly  the  same  volume  as  the  oxygen  from  which  it  was 
formed.  If  a  piece  of  burning  charcoal  had  been  used,  the  result 
would  have  been  the  same. 

193.  Ordinary  combustion  consists  in  the  union  of  combustible 
matter  with  oxygen,  and  is  usually  attended  by  the  evolution  of 
heat  and  light.  A  new  substance  is  also  formed,  which  may  be 
solid,  liquid,  or  gaseous.  When  iron  is  burned,  a  solid  product* 
(oxide  of  iron)  results,  which  just  equals  the  weight  of  the  iron 
and  oxygen  together,  that  have  .disappeared  during  the  opera- 
tion. It  is  evident  that  in  every  case  the  product  of  the  com- 
bustion must  be  equal  in  weight  to  that  of  the  oxygen  and  other 
substance  which  have  combined. 

Combustion  may,  however,   be  produced  without  oxygen;    a 

QUESTIONS, — How  may  iron  and  steel  be  made  to  burn  in  the  gas  ? 
What  is  produced  when  iron  is  burned  in  this  way  ?  Why  does  thi 
water  rise  in  the  receiver  as  the  combustion  progresses  ?  Why  is  not 
the  same  effect  produced  when  a  candle  is  made  to  burn  in  the  gas? 
193.  What  is  ordinary  combustion?  May  combustion  be  producec 
without  oxygen  ? 


180 


OXYGEN. 


piece  of  phosphorus  or  powdered  antimony,  let/  down  into  a 
receiver  filled  with  chlorine,  will  take  fire  spontaneously,  and 
burn  with  the  evolution  of  light  and  heat;  so  that  ordinary  com- 
bustion can  only  be  considered  as  a  particular  case  of  chemical 
action. 

Combustion  is  the  great  source  of  artificial  heat  and  light 
(13,  65).  To  produce  an  intense  heat  means  are  contrived  to 
force  large  quantities  of  air  (one-fifth  of  which  is  oxygen)  in 
contact  with  a  mass  of  ignited  coal,  the  carbonic  acid  formed 
being  allowed  to  escape  freely.  To  produce  light,  we  burn  oil, 
tallow,  or  .other  substances  which  contain  a  large  proportion  of 
the  same  material  as  coal,  as  we  shall  see  hereafter.  By  sup- 
plying the  burning  body  witli  pure  oxygen,  the  intensity  of  both 
the  heat  and  light  is  greatly  increased.  A  very  considerable 

heat  is  also  produced,  simply 
by  blowing  with  a  proper 
blowpipe  through  the  flame 
of  a  lamp  or  candle,  which 
is  sufficient  for  numerous  small  operations. 

A  better  form  of  the  blowpipe  is  represented  in  the  next  figure. 


Blowpipe. 


Mouth  Blowpipe. 

The  enlargement  at  the  angle  is  designed  to  retain  auy  moisture 

that  may  enter  the  tube  from  the 
mouth. . 

In  using  the  blowpipe  the  flame 
is  driven  violently  to  one  side,  as 
shown  in  the  figure;  and  the 
greatest  heat  is  found  just  be- 
yond the  point  of  the  inner  flame. 
Blowpipe  Flame.  If  pure  oxygen  is  used  with  the 

QUESTIONS. — What  is  the  great  source  of  artificial  light  and  heat? 
"What  substances  do  we  use  for  fuel  when  light  is  to  be  produced  ?  What 
is  the  use  of  the  blowpipe  ?  At  what  point  in  the  flame  is  the  heat 
greatest  ? 


HYDROGEN.  181 

blowpipe,  instead  of  atmospheric  air,  as  may  easily  be  done,  the 
heat  produced  becomes  much  more  intense. 

194,  Respiration  is  also  supported,  by  oxygen  gas,  which   is 
absolufely  essential  to  the  process;   no  animal  can  live  in  an 
atmosphere  that  does  not  contain  it.     A  small  animal,  as  a  bird, 
confined  in  a  close  box,  feels  no  inconvenience  for  a  time ;  but 
the  oxygen  gradually  is  absorbed,  carbonic   acid  gas  taking  its 
place,  and  respiration  becomes  laborious,  until  at  length  the  ani- 
mal dies  for  the  want  of  oxygen.     Pure  oxygen,  however,  does 
not  .answer  the   purposes  of  respiration,  as  it  excites   the  vital 
action  too  much,  producing  various  inflammatory  symptoms,  and 
at  length  death,  as  the  result  of  the  over-action. 

195.  Manipulation  of  Gases. — The  general  method  of  collecting  oxygen, 
described  above,  answers  for  all  the  gases  that  are  not  absorbed  by- 
water.     In  the  same  mode,  also,  a  gas  may  be  transferred  from  one 
receiver  to  another.     When  a  gas  is  to  be  collected  that  is  largely  ab- 
sorbed by  water,  some  other  liquid  must  Jbe  used,  as  mercury,  or  a 
saturated  solution  of  salt ;  or  the  air  may  b*e  removed  by  the  air-pump, 
and  then  the  gas  admitted. 


HYDROGEN. 

Symbol,  H;  Equivalent,  1;  Density,  0- 

196.  History.— This  gas  was  first  described  by  Cavendish  in 
1766,  and  received  from  him  the  name  of  inflammable  air,  be- 
cause  of  its  combustibility.      It  has  received  its  present  name 
because  it  forms  a  part  of  water  (from  Jiudor,  water,  and  gennao, 
to  produce).     It  is  not  found  free  in  nature,  but  constitutes  one- 
niuth  part  of  water,  and  enters  into  nearly  all  animal  and  vege- 
table substances. ' 

197.  Preparation. — Hydrogen  gas  is  always  procured  by  the 
decomposition  of  water,  either  directly  or  indirectly.     The  direct 

QUESTIONS. — 194.  Is  oxygen  necessary  for  the  support  of  respiration? 
Will  pure  oxygen  answer  the  purpose?  195.  What  is  meant  by  the 
rminipulatiori  of  the  gases  ?  When  a  gas  is  to  be  collected  that  is  largely 
absorbed  by  water  what  is  the  course  to  be  pursued*?  196.  What  facts 
are  mentioned  in  the  history  of  hydrogen?  Why  has  it  been  called 
inflammable  air?  Why  is  it  now  called "~hy drogenl  197.  From  what  is 
this  gas  always  prepared  ? 
16 


182 


HYDROGEN. 


method  consists  in  passing  the  vapor  of  water  over  metallic  iron, 
heated  to  redness.  This  is  done  hy  putting  iron  wire  or  turnings 
into  a  gun-barrel  open  at  hoth  ends,  to  one  of  which  is  attached 
a  retort  containing  pure  water,  and  to  the  other  a  bent  tube.  The 
gun-barrel  is  placed  in  a  furnace,  and  when  it  has  acquired  a  full 
red-heat,  the  water  in  the  retort  is  made  to  boil  briskly.  The 
gas,  which  is  copiously  disengaged  as  soon  as  the  steam  comes  in 
contact  with  the  glowing  iron,  passes  along  the  bent  tube,  and 
may  be  collected  in  convenient  vessels,  by  dipping  the  free 
extremity  of  the  tube  into  the  water  of  a  pneumatic  trough. 

The  arrangement 
of  the  apparatus  will 
be  seen  by  the  ac- 
companying figure. 
A  retort,  a,  con- 
tains the  water,  b  b 
is  the  furnace,  with 

Preparation  of  Hydrogen.  the    gun.barrel)  c  r> 

in  which  are  the  iron  turnings  to  be  heated,  and  at  the  left  is  the 

receiver  to  collect  the  gas  as  it  is  formed. 

The  second,   or  indirect  method,  which  is   the   one  usually 

adopted  in  practice,  consists  simply  in  dropping  pieces  of  zinc 
(or  iron)  into  sulphuric  acid,  diluted 
with  five  or  six  times  its  weight  of 
water,  and  contained  in  a  convenient  re- 
tort. Action  immediately  commences, 
without  the  aid  of  heat,  and  the  gas 
may  be  collected  over  water.  A  jar 
prepared  as  in  the  figure  is  very  con- 
venient  for  the  purpose.  The  water 
and  zinc  are  first  introduced,  and  after 

Preparation  of  Hydrogen.          ^    CQrk   wjth    the    tubeg    jg    carefully 

inserted  in  its  place,  the  acid  is  poured  in  through  the  long- 
necked  funnel.  The  gas  is  collected  by  means  of  a  tube  leading 
from  the  cover  to  a  receiver,  as  before. 


QUESTIONS. — Describe  the  mode  first  mentioned  of  preparing  hydrogen 
gas.     Describe  the  mode  by  the  use  of  dilute  sulphuric  acid  and  zinc- 


HYDROGEN. 


183 


Decomposition 
of  Water  by 
Potassium. 


Hydrogen  gas  is  also  very  readily  procured  by 
the  action  of  metallic  potassium  or  sodium  upon 
water.  A  small  receiver  is  first  filled  with  water, 
and  then  a  piece  of  the  metal,  wrapped  in  bibulous 
paper,  is  quickly  placed  under  it ;  as  soon  as  the 
paper  becomes  moistened,  violent  action  takes 
place,  and  the  hydrogen  that  is  liberated  rises  to 
the  upper  part  of  the  receiver.  This  method,  on 
account  of  the  high  price  of  potassium  and  sodium, 
is  very  expensive. 

198.  Properties, — Pure  hydrogen  gas  is  without  color,  odor,  or 
taste,  and  refracts  light  powerfully.  It  has  never  yet  been  reduced 
to  the  liquid  state.  It  does  not  support  respiration,  but  may  be 
breathed,  when  mixed  with  air,  without  injury. 

It  is  the  lightest  substance  known,  being  sixteen  times  lighter 
than  oxygen,  and  more'  than  fourteen  times 
lighter  than  atmospheric  air,  100  cubic 
inches  weighing  only  2-14  grains.  Soap- 
bubbles  filled  with  it  rise  readily  through 
the  air.  They  may  be  formed  very  easily 
by  attaching  a  common  tobacco-pipe  by  its 
stem  to  a  gas-bottle  filled  with  the  gas,  and 
forcing  out  the  gas  slowly,  immediately  SoaP Bubbles  with  Hydrogen- 
after  dipping  the  mouth  of  the  pipe  in  a  strong  solution  of  soap 
in  warm  water. 

Hydrogen  gas  is  eminently  combustible,  and 
burns  with  a  feeble  yellowish  flame.  This  may 
be  shown  by  pouring  some  dilute  sulphuric  acid 
upon  some  pieces  of  zinc  in  a  vial,  and  inserting  a 
cork  with  a  small  glass  tube  or  pipe-stem,  as  shown 
in  the  accompanying  figure.  In  a  short  time  a  jet 
of  hydrogen  will  issue  from  the  tube,  and  may  be 
inflamed.  This  is  often  described  as  the  philoso- 
phical candle. 

QUESTIONS. — Describe  the  mode  of  preparing  hydrogen  by  the  use 
of  metallic  potassium.     198.  Mention  some  of  the  properties  of  hydrogen. 
What  is  the  weight  of  100  cubic  inches  of  the  gas  ?     What  is  said  of  soap- 
bubbles  formed  with  it  ?     How  may  it  be  shown  that  the 
bustible  ? 


Hydrogen  Com- 
bustible. 


of  soap- 
s  is  com- 


1&4 


HYDROGEN. 


If,  now,  as  the  jet  continues  to  burn,  a  glass  tube, 
half  an  inch  or  more  in  diameter,  and  one  or  two 
^Ge*  ^on&>  ^6  keld  °ver  it,  and  properly  managed, 
a  clear  musical  note  will  be  produced,  its  pitch  de- 
pending upon  the  length  and  diameter  of  the  tube. 
It  is  occasioned  by  successive  explosions  within  the 
tube,  which  follow  each  other  so  rapidly  as  to  cause 
the  air  in  the  tube  to  vibrate,  as  in  a  musical  instru- 
ment. 

The  following  is  an  interesting  and  instructive  ex- 
periment with  this  gas.     Let  a  bell-glass  receiver  be 
^e^  witn  ^  in  the  pneumatic  cistern,  and  then,  care- 
Sound*,     fully^lifting  it  with  the  left  hand,  with  the  right  hand 
paes  up  into  the  interior  a  lighted  candle,  as  re-presented  in  the 
annexed  figure.     As  the  flame    enters  the 
hydrogen,   it  will    take   fire  with    a    slight 
explosion,  and  continue  to  burn  where  it  is 
in    contact  with    the   air;    but   the    candle 
being  carried  farther  upward  into  the  pure 
hydrogen,  will  be  extinguished.     The  hy- 
drogen, being  qombustible,   is   inflamed   by 
the   burning  candle,  but  not  being  a  sup- 
porter of  combustion,  the  candle   is   extin- 
guished as  soon  as  it  is  surrounded  by  it. 
The  gas   is  retained  in   the  receiver  when 
lifted  from  its  place,  because  of  its  being  so 

Hydrogen  not  a  Supporter,  much  lighter  than  air. 

199.  Hydrogen,  being  the  lightest  substance  known,  is  made  use  of  by 
aeronauts  for  filling  their  balloons.  The  buoyancy  of  a  balloon  filled 
with  it  is  easily  calculated.  Thus,  100  cubic  inches  of  air  weighing 
31  grains,  the  weight  of  a  cubic  foot  will  be  535-68  grains,  while 
the  weight  of  an  equal  volume  of  hydrogen  will  be  but  36-98  grains. 
Now  535-68 — 36-98  =  498-70  grains.  This  number  multiplied  by  the 
number  of  cubic  feet  in  a  balloon,  will  give  in  Troy  grains  the  weigh, 
required  to  be  added  to  make  it  of  equal  weight  with  the  air  displaced ; 

QUESTIONS. — Describe  the  mode  of  producing  musical  sounds.  How 
may  it  be  shown  that  the  gas  does  not  support  combustion  ?  Will  the 
hydrogen  itself  be  inflamed  in  the  experiment?  199.  Why  is  hydrogen 
selected  for  filling  balloons?  Describe  the  method  of  calculating  the 
weight  a  tolloon  will  sustain  in  the  air.  . 


COMPOUNDS   OF   HYDROGEN   AND   OXYGEN.  185 

and  if  it  is  loaded  with  anything  less  than  this  it  will  ascend.     The  weight 
of  the  balloon  itself  is  of  course  always  to  be  taken  into  the  account. 

Coal  gas  being  always  on  hand  where  there  are  gas-works,  though  much 
heavier  than  hydrogen,  is  now  much  used  in  balloons  in  consequence 
of  its  being  cheaper,  the  balloon  being  of  course  made  proportionally 
larger. 


Compounds  of  Hydrogen  and  Oxygen. 

There  are  only  two  compounds  of  these  substances  known,  the 
protoxide,  or  water,  and  the  peroxide ;  and  the  latter  is  alto- 
gether an  artificial  product,  of  difficult  formation. 

200.  Protoxide  of  Hydrogen,  or  Water. — HO,  or  Aq. ;   eq., 

(1  -f  8  =)  9, — This  compound,  considered  in  all  its  important 
relations,  and  absolutely  universal  diffusion,  is  probably  the  most 
important  substance  known  to  man.  It  is  the  sole  product  of  the 
combustion  of  hydrogen,  whether  in  the  open  air  or  mixed  with 
oxygen  gas.  In  the  experiment  for  producing  musical  sounds, 
the  water  that  is  formed  will  be  seen  to  condense  in  considerable 
quantity  on  the  inside  of  the  glass  tube,  at  the  beginning  of  the 
process,  but  it  will  be  evaporated  when  the  tube  becomes  hot. 

The  affinity  of  hydrogen  for  oxygen  is  very  great,  but  the  two 
gases  do  not  combine  spontaneously,  even  if  kept  together  for  any 
length  of  time.  We  have  seen  above  (162)  that  two  measures 
of  hydrogen  combine  with  exactly  one  measure  of  oxygen ;  and 
the  mixture  may  be  exploded  by  the  approach  of  flame,  by  the 
electric  spark,  by  intensely  heated  metal,  or  by  the  mere  presence 
of  spongy  platinum,  a  substance  that  will  be  described  hereafter. 
To  explode  the  mixed  gases  by  the  electric  spark,  the  spark  must 
^e  made  to  pass  through  them.  This  is  accomplished  in  the 
following  manner.  A  small  metallic 
vessel,  as  a  miniature  cannon,  has  a 
metallic  wire,  W,  inserted  in  one  side 
through  a  piece  of  wood  or  .ivory,  so  Hydrogen  Pistol. 

AS  to  extend  nearly  through  to  the  other  side,  as  shown  in  the  figure. 

QUESTIONS. — Why  is  coal  gas  now  often  used  as  a  substitute  foi 
hydrogen  in  filling  balloons  ?  How  many  compounds  of  hydrogen  and 
oxygen  are  known?  200.  What  is  protoxide  of  hydrogen?  What  is 
said  of  the  affinity  of  hydrogen  for  oxygen  ?  In  what  proportion  do  they 
combine  by  measure  ?  By  weight?  How  may  the  mixed  gases  be  exploded  t 
16* 


186  COMPOUNDS   OF   HYDROGEN   AND   OXYCJEN. 

The  piece  is  then  to  be  filled  with  the  proper  mixture  of  the  gases, 
and  a  cork,  C,  inserted  in  the  muzzle.  If,  now,  a  spark  of  elec- 
tricity be  communicated  to  the  ball  of  the  wire  W,  in  escaping 
from  the  other  end  it  ignites  the  gases,  and  the  cork  is  forced  out 
with  a  loud  report.  If  a  mixture  of  equal  parts  of  hydrogen  and 
atmospheric  air  is  used,  the  effect  will  be  nearly  the  same. 

The  explosion  which  accompanies  the  union  of  these  gases  is 
occasioned  by  the  great  expansion  of  the  gases  at  the  rnomen 
of  combination,  in  consequence  of  the  heat  developed.  This  is 
the  only  rational  explanation  that  can  be  given,  and  yet  it  is  a 
fact  that  this  combination  is  attended  by  a  contraction  of  one- 
third  of  the  volume  of  the  mixed  gases  in  forming  the  vapor  of 
water,  (162)  to  say  nothing  of  the  still  greater  contraction  which 
takes  place  by  the  condensation  of  the  steam  that  is  found. 

This  expansion  takes  place  apparently  with  great  violence ;  but 
by  using  a  strong  receiver  for  the  mixed  gases  it  may  be  restrained, 
and  then  the  combination  takes  place 
without  any  report.  The  figure  in  the 
margin  represents  a  piece  of  apparatus 
for  this  purpose.  A  strong  glass  globe 
three  or  four  inches  in  diameter  has  a 
metallic  cap  upon  the  neck,  upon  which 
a  cover  is  firmly  screwed  after  the  mixed 

No  Explosion.  ,         .        _.  ,       .  , 

gases  are  introduced.     From  each  side 

of  the  globe  is  a  projection  or  neck,  with  a  metallic  cap,  through 
which  wires  are  inserted  so  as  nearly  to  meet  in  the  centre.  When 
the  globe  is  charged  with  the  mixed  gases  the  electric  spark  is 
passed  between  these  wires,  and  the  gases  at  once  combine,  but 
without  explosion,  a  slight  flame  only  being  seen  at  the  instant. 
The  inside  of  the  glass  becomes  covered  with  dew  from  the 
moisture  produced,  and  when  the  cover  is  unscrewed  the  rushing 
in  of  the  air  attests  the  vacuum  that  has  been  formed. 

The  ignition  of  hydrogen  by  spongy  platinum  is  well  shown  by 
holding  a  small  piece  of  this  substance  in  a  jet  of  the  gas,  by 
means  of  a  small  wire  twisted  round  it.  The  platinum  must  be 

QUESTIONS. — Describe  the  pistol  for  exploding  the  gases  by  the  electric 
Bpark.  What  occasions  the  great  expansion  that  takes  place?  May  the 
jjases  be  made  to  unite  without  an  explosion  ? 


COMPOUNDS  OF  HYDROGEN  AND  OXYGEN. 


187 


Fire  Apparatus. 


perfectly  dry.  It  gradually  becomes  heated  to  redness,  and  soon 
the  jet  is  inflamed.  The  common  hydrogen  Jlre-apparatus  actl 
upon  this  principle.  Its  construction  is  shown  in 
the  figure  in  the  margin.  A  cylindrical  glass  ves- 
sel, A,  is  partly  filled  with  dilute  sulphuric  acid, 
and  in  it  is  a  small  glass  receiver,  B,  firmly  ce- 
mented at  the  top  into  a  cap  connected  with  the 
brass  cover.  By  the  action  of  the  acid  upon  a 
piece  of  zinc,  Z,  suspended  inside  of  this  receiver 
near  the  bottom,  it  is  soon  filled  with  hydrogen 
gas,  which,  on  jurning*lhe  faucet  F,  is  forced  out 
by  the  rise  of  the  liquid  upon  a  piece  of  platinum 
sponge,  contained  in  the  cup  0.  Soon  the  platinum  is  heated  so 
as  to  inflame  the  jet  of  hydrogen,  from  which  a  candle  can  be 
at  once  lighted.  The  platinum  sponge  often 
loses  its  property  of  inflaming  hydrogen, 
but  recovers  it  again  by  being  heated. 

A  metallic  cup  of  half  a  pint  capacity 
filled  with  the  mixed  gases  and  inverted 
over  a  small  piece  of  platinum  sponge,  sup- 
ported a  little  above  the  table  by  a  wire, 
will  be  thrown  upward  to  the  ceiling  by  the 
explosion  produced. 

201.    The  compound  blowpipe,  which  is 
an  invention  of  Dr.  Hare  of  Philadelphia, 
is  a  contrivance  by  which  two  jets,  one  of 
hydrogen  and  another  of  oxygen,  are  made 
tc  issue  together,  and  are  inflamed  as  they  escape.     The  gases  are 
brought   by  tubes   from   separate 
gas-holders,  so  as  to  discharge,  as 
near  as  may  be,  two  measures  of 
hydrogen  to  one  of  oxygen.     The 
heat  produced  by  this  instrument 
is  very  great,  probably  exceeding 
that  produced  by  any  other  means.  Compom]d  Blowp.pe> 

QUKSTIONS. — Describe  the  hydrogen  fire  apparatus.  Describe  the -ex 
periment  with  the  spongy  platinum  and  the  metallic  cup.  201.  Describe 
the  compound  blowpipe.  What  is  said  of  the  heat  which  is  produced? 


Explosion. 


188  COMPOUNDS   OP   HYDROGEN   AND   OXYGEN. 

Platinum  and  other  substances  incapable  of  fusion  in  the  hottest 
furnaces,  are  melted,  and  often  even  volatilized  by  it.  A  small 
piece  of  lime,  held  in  the  flame,  becomes  intensely  heated,  and 
glows  with  a  brilliant  light,  exceeding  any  other  that  can  be  pro- 
duced artificially.  It  is  known  under  the  name  of  the  Drum- 
mond  tight,  and  is  much  used  for  practical  purposes. 

202.  Water,  at  ordinary  temperatures,  is  a  transparent,  color- 
less  liquid,  without  taste  or  smell.     In  the  open  air,  it  boils  at  a 
temperature  of  212°,  and  freezes  at  32°.     The  vapor  produced  by 
boiling,  familiarly  called  steam,  is  perfectly  colorless  and  trans- 
parent, and  has  a  density  of  0-622,  air  befibg  1 ;  100  cubic  inches 
weighing  19-28  grs.     In  the  form  of  ice,  its  density  is  0-92.     A 
cubic  inch  of  pure  water  weighs  252-458  grs.,  being  814  times 
as  much  as  an  equal  volume  of  air  would  weigh.     A  cubic  foot 
weighs  1000  oz.,  or  62  £  Ibs.  avoirdupois.      Water  is  probably 
the    most    powerful    solvent    known.       It    is    capable   of   com- 
bining, in  definite  proportions,  with  many  substances,  forming 
compounds  which  yet  remain  perfectly  dry.     They  are  usually 
called   Jiydrates.      Substances  from  which   all  water  has  been 
separated  are  said  to  be  anhydrous. 

Water  is  never  found  naturally  perfectly  pure ;  that  of  wells, 
springs,  and  rivers  always  contains  carbonic  acid  and  saline  matter 
in  solution,  obtained  while  percolating  through  the  soil;  and  that 
from  rain  or  snow  is  impregnated  with  air  and  oxygen,  and  some- 
times with  other  gases.  It  is  obtained  pure  only  by  distillation ; 
and  even  then,  by  standing  for  a  time,  it  takes  up  more  or  less 
atmospheric  air,  which,  however,  does  not  unfit  it  for  the  ordi- 
nary operations  of  the  laboratory  in  which  it  is  required. 

203.  Water  when  it  solidifies  often  forms  beautiful  crystals 
(25)  which  are  best  seen  in  snow  and  frost; — in  ordinary  ice 
they  cannot  usually  be  seen,  though  it  is  believed  there  is  always 

QUESTIONS. — What  is  said  of  the  light  produced  -when  a  piece  of  lime 
is  held  in  the flarne ?  By  what  name  is  this  light  known?  202.  What 
is  said  of  wate^  at  ordinary  temperatures  ?  What  are  its  freezing  and 
boiling  points?  What  is  steam?  What  is  its  density?  What  is  the 
density  of  ice?  What  is  the  weight  of  a  cubic  inch  of  water?  How 
many  times  is  it  heavier  than  air  ?  What  are  the  chemical  compounds 
of -water  called  ?  Is  water  ever  found  perfectly  pure  in  nature  *  How 
only  is  pure  water  obtained  ?  203.  When  water  solidifies  does  it  take 
the  form  of  crystals  ? 


COMPOUNDS  OF.  HYDROGEN  AND  OXYGEN.       189 

a  proper  crystaline  arrangement.  The  primary  crystals  belong  to 
the  hexagonal  system  (178-6),  but  they  are  often  grouped  to- 
gether iu  various  modes,  as  shown  in  the  figures.  Nos.  3, 4,  5,  6;  7, 


Crystals  of  Ice. 


and  f  fire  more  common  than  the  simple  forms  Nos.  1  and  2. 
Thej>«  ^tter  are  of  more  frequent  occurrence  in  hoar-frost  than 
in  sno-w. 

204.  The  different  processes  for  procuring  hydrogen,  given 
above,  require  some  further  explanation,  before  we  dismiss  this 
subject.  Ihe  first  method  is  founded  on  the  fact  that  iron,  at  high 
temperatures,  decomposes  water  when  presented  to  it  in  the  form 
of  steam,  the  oxygen  combining  with  the  iron  to  form  protoxide 
of  iron,  and  the  hydrogen  being  set  free.  The  changes  are  thus 
represented : 

HO  +  Fe  =  FeO  +  H. 

The  changes  which  take  place  in  the  second  and  more  common 
process  for  piocuring  this  gas,  are  more  complicated.  They  are 
represented  in  the  following  formula.  Thus, 

HO,S03  +  Zn  =  ZnO,S03  +  H. 

In  this  case  it  /rill  still  be  seen  that  it  is  the  water  which  supplies 
the  hydrogen.  The  oxygen  of  the  water  is  transferred  to  the 
zinc,  forming  protoxide  of  zinc,  with  which  the  sulphuric  acid 
immediately  combines.  When  a  piece  of  clean  zinc  is  immersed 

QUESTIONS. — What  is  said  of  frost  and  snow?  204.  Explain  the 
several  modes  of  procuring  hydrogen,  and  write  the  equations  illustrating 
the  reactions  that  take  place. 


t 

190  COMPOUNDS   OP   HYDROGEN   AND   OXYGEN. 

in  water,  little  action  takes  place,  because  the  outside  becomes 
coated  with  a  thin  film  of  oxide  of  zinc,  which  is  insoluble  in 
water;  but  if  sulphuric  acid  is  present,  this  oxide  is  instantly 
dissolved,  and  thus  a  clean  surface  constantly  exposed  to  the 
water. 

In  the  third  process,  the  metal  itself  at  once  decomposes  a  por- 
tion of  the  water,  forming  a  soluble  oxide  of.  the  metal,  and  libe- 
rating the  hydrogen.  Thus, 


Here  the  affinity  of  metallic  potassium  for  oxygen  is  sufficient 
to  separate  this  element  from  its  union  with   hydrogen  in  the 
water,   forming   oxide   of  potassium    or   potassa. 
^      Great  heat  is  produced   by  the  action,  and  the 
hydrogen  liberated  is  inflamed  if  the  experiment 
is  made  in  the  open  air.     To  show  this  all  that  is 
necessary  is  to  throw  a  small  piece  of  potassium 
Potassium  inflamed  uPon  the  surface  of  some  water,  as  shown  in  the 

by  water.  figure. 

The  mode  of  decomposing  water  by  the  galvanic  current  has  already 
(111)  been  explained. 

205.  Knowing  that  water  is  formed  by  the  union  of  2  volumes  of  hy- 
drogen and  1  volume  of  oxygen  condensed  into  2  volumes  of  steam, 
it  is  easy  to  calculate  the  density  of  steam,  and  also  the  quantity  of  each 
of  these  elements  in  a  given  quantity  of  water.  Thus, 

One  volume  of  oxygen  weighs  1-106 

Two         "         hydrogen"      2x069  =  0-138 


Two         "        steam         "  1-244 

One-half  of  this  sum,  or  -622,  is  then  the  density  of  the  vapor  of  water 
which  is  formed. 

To  calculate  the  quantity  of  each  of  the  elements  in  100  parts  of  water 
we  have 

1-244  :  1-106  :  :  100  :  z, 

whence    x  —  88-9  =  quantity  pf  oxygen. 
And  100—  89-9  =  11-1  =  quantity  of  hydrogen. 


QUESTIONS. — Is  heat  produced  when  water  is  decomposed  by  potas- 
sium? 205.  What  is  the  density  of  steam?  Describe  the  mode  of  cal- 
culating it. 


NITROGEN. 


191 


208.  Peroxide  of  Hydrogen—  H02 ;  eq.,  (1  -f  16  =  )  17.— Thia  Bub- 
tance  has  been  obtained  only  in  the  liquid  form,  and  when  most  con- 
centrated possesses  a  specific  gravity  of  1-452.  It  is  colorless,  trans- 
parent, and  without  odor.  It  is  sometimes  called  oxygenized  water.  ^ 

Though  it  differs  from  water  only  in  containing  an  additional  equiva- 
lent of  oxygen,  it  acts  powerfully  upon  the  skin,  producing  a  prickling 
sensation,  whitening  the  surface,  and  destroying  the  texture,  if  the  appli- 
cation is  long  continued. 

If  the  temperature  is  raised  as  high  as  59°,  it  is  decomposed  and  con- 
verted into  water  and  oxygen  gas ;  a  sudden  elevation  of  temperature 
even  causes  an  explosion.  It  is  also  decomposed  by  the  action  of  nearly 
all  the  metals,  and  many  of  the  metallic  oxides.  Diluted  with  water  or 
mixed  with  some  acid,  it  is  less  liable  to  decomposition  than  when  pure. 


NITROGEN. 
Symbol,  N;  Equivalent,  14;  Density,  0-972. 

207.  History. — The  existence  of  this  element  has  been  known 
since  1772 ;  and  it  was  recognized  as  a  constituent  of  the  atmo- 
sphere in  1775.     It  was  first  called  azote  (from  a,  privitive,  and 
zoe,  life),  because  it  does  not  support  respiration ;  it  receives  its  pre- 
sent name  from  the  circumstance  that  it  forms  an  ingredient  of  nitre. 

208.  Preparation. — Nitrogen  gas  is  readily  prepared,  nearly 
pure,  by  burning  a  piece  of  phosphorus  in  a  receiver  over  water. 
A   small   c-up,   C,   containing   a   piece   of 

phosphorus,  is  placed  upon  the  surface  of 
the  water  in  the  pneumatic  cistern,  the 
phosphorus  ignited,  and  the  receiver  then 
placed  over  it.  The  phosphorus  continues 
to  burn,  absorbing  all  the  oxygen,  and  the 
water  rises  to  supply  its  place,  as  shown  in 
the  figure.  The  glass  will  at  first  be  filled 
with  phosphoric  acid  fumes,  which  how- 
ever will  soon  be  absorbed  by  the  water. 
Some  vapor  of  phosphorus,  carbonic  acid, 
and  perhaps  a  trace  of  other  gases,  may  be  contained  in  the 

QUESTIONS. — 206.  What  is  peroxide  of  hydrogen?  What  are  some 
of  its  properties  ?  207.  How  long  has  nitrogen  been  known  ?  What  waa 
it  first  called  ?  '  Why  has  it  received  its  present  name  ?  208,  Describe 
the  mode  of  preparing  nitrogen. 


Preparation  of  Nitrogen. 


192  A.T  MO  SPHERIC    AIR. 

nitrogen  thus  prepared,  but  it  will  be  found  sufficiently  pure  for 
nearly  all  purposes.  Other  processes  might  be  described  for  pro- 
curing it,  as  by  passing  a  current  of  chlorine  gas  through  strong 
aqua  ammonia,  but  the  above  is  the  most  speedy  and  convenient. 

209.  Properties. — Pure   nitrogen   is   a   colorless   gas,  wholly 
devoid  of  smell  and  taste,  and  is  distinguished  from  other  gases 
more  by  negative  characters  than  by  any  striking  quality.     It  is 
Hot  a  supporter  of\  combustion,  but,  on  the  contrary,  extinguishes 
all  burning  bodies  that  are  immersed  in  it.      A 
taper  immersed  in  it  is  extinguished  at  once.     No 
animal  can  live  in  it;  but  yet  it  exerts  no  injurious 
action  either  on  the  lungs  or  on  the  system  at  large, 
the  privation  of  oxygen  gas  being  the  sole- cause 
of  death.     It  is  not  inflammable,  like  hydrogen  ; 
though,  under  favorable  circumstanc.es,  it  may  be 
made  to  unite  with  ox}-gen.      It  is  slightly  dis- 
solved by  water,  and  is  sometimes  found  in  the 
water  of  mineral  springs,  as  at  Lebanon,  in  the 
State  of  New  York.    100  cubic  inches  of  the  gas 
DoceoSmb°u8fioPnP.ort  weigh  3016  grs.,  giving  a  specific  gravity  of  0-97. 


Atmospheric  Air. 

210.  The  earth  is  everywhere  surrounded  by  a  mass  of  gaseous 
matter,  .called  tbe  atmosphere,  which  is  preserved  at  its  surface 
by  the  force  of  gravity,  and  revolves  with  it  around  the  sun.  It 
is  colorless  and  invisible,  excites  neither  taste  norx  smell  when 
pure,  and  is  not  sensible  to  the  touch,  unless  when  it  is  in  motion. 
It  possesses  the  physical  properties  of  elastic  fluids  in  a  high 
degree.  Its  specific  gravity  is  unity  (1),  being  the  standard  with 
which  the  density  of  all  gaseous  substances  is  compared.  It  is 
814  times  lighter  than  water,  and  nearly  11,065  times  lighter 
than  mercury,  100  cubic  inches  weighing  31  grs. 

QUESTIONS. — Is  the  nitrogen  thus  obtained  pure  ?  '  209.  What  are 
some  of  the  properties  of  nitrogen?  210.  What  is  the  atmosphere? 
"What  are  some  of  the  properties  of  atmospheric  air?  What  is  the 
weight  of  100  cubic  inches  ? 


, 


ATMOSPHERIC    AIR. 


193 


Atmospheric  air  is  composed  of  nitrogen  and  oxygen,  with  a 
variable  proportion  of  carbonic  acid  and  watery  vapor,  and  usually 
a  trace  of  ammonia.  Besides  these,  there  may  occasionally  be 
other  substances  present,  depending  upon  local  causes,  as  the 
odoriferous  principle  of  plants,  and  the  miasmata  of  marshes, 
which  is  supposed  to  be  the  chief  cause  of  disease  in  many  un- 
healthy situations ;  but  they  cannot  be  detected  by  chemical  tests. 
,  Instruments  for  determining  the  relative  pro- 
portion of  the-  gases  composing  the  atmosphere 
are  called  eudiometers.  The  following  con- 
trivance answers  the  purpose  very  well.  Let  a 
glass  tube,  closed  at  one  end,  and  graduated  to 
100  parts,  with  a  small  piece  of  phosphorus  sup- 
ported in  it  on  a  wire  near  the  top,  be  placed  as 
in  the  figure,  with  the  open  end  immersed  in  a 
vessel  of  water.  The  phosphorus  gradually  ab- 
sorbs the  oxygen  of  the  air  in  the  tube,  and  the 
water  rises  to  supply  its'  place.  In  one  or  two 
days,  depending  upon  the  temperature,  the  ab- 
sorption will  be  complete;  and  the  number 
of  the  division  of  the  tube  now  filled  with 
water  will  indicate  the  proportion  of  oxygen. 

By  the  above  and  other  similar  modes  of  analysis,  it  is  found 
that  the  atmosphere  in  100  parts  is  composed  of — 

By  Weight.  By  Measure. 

Nitrogen 76-9  79-3 

Oxygen 23-1  20-7 

100  100 

The  proportion  of  carbonic  acid  varies  from  2  to  6  parts  in  10,000 
of  air.  A  trace  of  ammonia  is  not  unfrequently  found,  and  also 
of  carbureted  hydrogen. 

The  atmosphere  is  believed  to  extend  to  the  height  of  about 
forty-five  miles,  becoming  continually  less  and  less  dense  from  the 

QUESTIONS. — What  is  atmospheric  air  composed  of?  What  other  gases 
are  also  found  in  it  ?  What  is  the  design  of  eudiometers  ?  Describe  the 
mode  of  determining  the  proportion  of  oxygen  by  means  of  phosphorus. 
What  is  thus  found  to  be  the  quantity  of  oxygen  in  100  parts  of  air? 
What  is  the  usual  quantity  of  carbonic  acid  in  10,000  parts  of  air! 
What  is  the  height  of  the  atmosphere  ? 


Eudiometer. 


194  ATMOSPHERIC    AIR. 

surface  upward ;  and  presses  by  its  gravity  upon  the  surface  with 
a  force  equal,  ordinarily,  to  about  15  Ibs.  to  the  square  inch.  It 
is  capable  of  supporting  a  column  of  water  about  34  feet,  and.  a 
column  of  mercury  about  30  inches  in  perpendicular  height. 

211.  Atmospheric  air  is  highly  compressible  and  elastic,  so  that 
its  particles  admit  of  being  approximated  to  a  great  extent  by 
compression,  and  expand  to  an  extreme  degree  of  rarity  when  the 
tendency  of  its  particles  to  separate  is  not  restrained  by  external 
force.     The  volume  of  air  and  all  other  gaseous  fluids,  so  Jong  as 
they  retain  the  elastic  state,  is  inversely  as  the  pressure  to  which 
they  are  exposed.      Thus  a  portion  of  air  which  occupies  100 
measures  when  compressed  by  the  ordinary  atmospheric  pressure, 
will  be  diminished  to  50  measures  when  the  pressure  is  doubled, 
and  will  expand  to  200  measures  when  the  compression  is  reduced 
to  one-half.     But  those  gases  which  are  susceptible  of  condensa- 
tion by  pressure  into  the  liquid  form,  as  the  pressure  approaches 
this  point,  vary  from  the  law,  the  volume  diminishing  more  rapidly 
than  this  would  indicate. 

The  chief  chemical  properties  of  the  atmosphere  are  owing  to 
the  presence  of  oxygen  gas.  Air  from  which  this  principle  has 
been  withdrawn,  is  nearly  inert.  It  can  no  longer  support  respi- 
ration and  combustion,  and  metals  are  not  oxydized  by  being 
heated  in  it.  The  uses  of  the  nitrogen  are  in  a  great  measure 
unknown.  It  has  been  supposed  to  act  as  a  mere  diluent  to  the 
oxygen ;  but  it  most  probably  serves  some  useful  purpose  in  the 
economy  of  animals  and  plants,  the  exact  nature  of  which  has  not 
been  discovered. 

212.  The  question  has  often  been  discussed,  whether  the  oxygen 
and  nitrogen  of  the  atmosphere  are  to  be  considered  as  chemically 
combined,  or  only  in  a  state  of  mixture ;   bu*.  the  latter  opinion 
now  generally  prevails.     It  has  been  supposed  that  if  they  are 
merely  in  a  state  of  mixture,  oxygen,  being  the  most  dense,  ought 

QUESTIONS. — To  what  height  will  the  atmosphere  support  a  column  • 
of  water?  Of  mercury?  211.  Is  atmospheric  air  compressible  and 
elastic  ?  What  is  said  of  the  volume  of  air  and  other  elastic  fluids  in 
relation  to  the  pressure  to  which  they  may  be  subjected  ?  To  what  ara 
the  chief  chemical  properties  of  atmospheric  air  owing?  212.  Are  the 
oxygen  and  nitrogen  of  the  air  to  be  considered  chemically  combined,  or 
only  in  mixture  ? 


COMPOUNDS   OF   NITROGEN   AND   OXYGEN.  195 

to  settle  towards  the  surface  of  the  earth ;  but  it  is  found  by 
experiment  that  gases,  whatever  may  be  their  relative  density, 
when  brought  in  contact,  mix  (89)  uniformly  with  each  other. 
The  mixture  of  the  gases  will  even  take  place  through  thin  mem- 
branes, (see  author's  Nat.  Phil.j  p.  22,)  whether  animal  or  vege- 
table; the  least  dense  of  the  gases  passing  the  most  rapidly. 

213.  There  is  still  one  circumstance  for  consideration  respecting 
the  atmosphere.  Since  oxygen  is  necessary  to  combustion,  to 
the  respiration  of  animals,  and  to  various  other  natural  operations, 
by  all  of  which  that  gas  is  withdrawn  from  the  air,  it  is  obvious 
that  its  quantity  would  gradually  diminish,  unless  the  tendency 
of  these  causes  were  counteracted  by  some  compensating  process. 
This,  to  some  considerable  extent,  is  accomplished  by  vegetation, 
as  it  is  found  that  healthy  plants,  under  the  influence  of  the  sun's 
light,  are  constantly  absorbing  carbonic  acid  from  the  air,  the 
carbon  of  which  is  retained,  while  the  oxygen  is  returned  to  the 
air,  as  we  have  before  seen  (191).  Still,  it  has  been  calculated 
that  the  loss  of  oxygen  employed  in  respiration,  over  the  whole 
surface  of  the  globe,  in  100  years,  would  not  exceed  ^^  part 
of  the  whole  quantity  contained  in  the  atmosphere. 


Compounds  of  Nitrogen  and  Oxygen. 

214.  Oxygen  combines  with  nitrogen  in  five  different  propor- 
tions, forming  the  compounds  NO,  N02,  N03;  N04,  and  N05;  the 
last  three  of  which  are  acids. 

215.  Protoxide  of  Nitro- 
gen, or  Nitrous    Oxide — 
NO;  eq.,  (14  +  8=)  22. 
— This  is  a  permanent,  col- 
orless gas,  of  a  sweetish  taste 
and  smell.    100  cubic  inches 

Of  it  Weigh  47-22   gr's.,  and  Preparation  of  Nitrous  Oxide. 

QUESTIONS. — 213.  Is  oxygen  constantly  absorbed  from  the  atmosphere 
by  combustion  and  by  the  respiration  of  animals  ?  By  what  reverse  pro- 
cess is  carbonic  acid  absorbed  and  oxygen  restored  to  the  atmosphere  ? 
214.  How  many  compounds  of  nitrogen  and  oxygen  are  there  ?  215.  De- 
scribe the  protoxide  of  nitrogen. 


196 


COMPOUNDS   OF   NITROGEN   AND   OXYGEN. 


its  density  therefore  is  1-527.  It  is  best  prepared  as  shown  in 
the  figure  on  the  preceding  page,  by  heating  nitrate  of  ammonia, 
by  means  of  a  spirit-lamp,  in  a  glass  retort  to  a  temperature 
of  450°  or  480°.  The  sole  products  of  the  operation,  when 
carefully  conducted,  so  as  not  to  raise  the  temperature  too  high, 
are  water  and  the  gas  in  question.  The  composition  of  nitrate 
of  ammonia  is  NII3,HO,N05— which  by  heat  is  converted  into 
2  atoms  of  the  nitrous  oxide  in  question  and  4  atoms  of  water. 
Thus, 

NH3,  HO,  N05  =  4  HO  +  2  NO. 

The  water  of  course  is  condensed  and  remains  with  that  in  the 
cistern,  while  the  gas  is  collected  as  in  other  cases.  It  is  slightly 
absorbed  by  water  and  should  not  therefore  be  allowed  to  remain 
in  contact  with  it. 

Some  substances  burn  in  this  gas  with  great  brilliancy,  as  a 
lighted  candle  and  phosphorus;  and  sometimes  the  combustion 

A  of  iron  wire  in  it  may  be  effected,  but  not 

without  difficulty.  By  a  pressure  of  about 
30  atmospheres,  at  a  temperature  of  82°,  it 
is  compressed  into  a  liquid,  which  freezes  or 
becomes  solid  at  about  150°  below  zero ;  and 
by  the  evaporation  of  this  solid,  a  tempera- 
ture considerably  lower  than  this  has  been 
attained. 

Its  action  on  the  system,  when  breathed, 
is  very  remarkable,  producing  a  species  of 
\  intoxication,  which  has  acquired  for  it  the 
Nitr°Combidstio8n.PPOrt8  name  of  laughing  gas.  In  a  few  cases,  when 
it  has  been  inspired,  injurious  effects  have  resulted  j  and  it  should 
never  be  breathed  but  with  caution. 

216.  The  analysis  of  nitrous  oxide  is  made  as  follows;  in  a  given 
quantity  of  the  gas  accurately  measured  introduce  a  piece  of  potassium, 
the  gas  being  contained  in  a  glass  tube  closed  at  one  end  and  a  little  bent, 

QUESTIONS. — How  is  the  protoxide  of  nitrogen  prepared  ?  Describe 
the  chemical  changes  that  take  place,  and  write  the  equation  illustrating 
them.  Is  this  gas  absorbed  by  water?  Will  it  support  combustion? 
What  is  said  of  its  effects  upon  the  system  when  breathed  ?  216.  De- 
scribe the  mode  of  analyzing  this  gas. 


COMPOUNDS   OF   NITROGEN   AND   OXYGEN. 


197 


(263)  so  as  to  retain  the  potassium  while  the  open  end  is  immersed  in  mer- 
cury. Now  apply  the  heat  of  a  lamp  and  the  potassium  takes  fire  imme- 
diately, absorbing  all  the  oxygen  and  leaving  the  nitrogen.  This  being 
returned  to  the  gi'aduated  tube  in  which  the  gas  was  first  measured,  will 
be  found  to  have  the  same  volume  as  at  first.  We  learn  therefore  that  the 
protoxide  of  nitrogen  occupies  precisely  the  same  volume  as  the  nitro- 
gen contained  in  it  would  alone  occupy.  Now, 

One  volume  of  the  protoxide  weighs   1-527 
One         "        "       nitrogen  (subtract)    '972 


Half 


oxygen,  very  nearly,  -555 


Nitrous  oxide  is  therefore  a  compound  of  1  volume  of  nitrogen  and  J 
volume  of  oxygen,  the  whole  condensed  into  1  volume. 

The  same  result  is  obtained  by  passing  a  quantity  of  the  gas  through 
a  heated  porcelain  tube  by  which  it  is  decomposed,  and  1  volume  of 
nitrogen  and  £  volume  of  oxygen  obtained. 

217.  Binoxide  of  Nitrogen,  or  Nitric  Oxide  —  N02;  eq., 
(14  +  16  =)  30. — This  is  also  a  gaseous  substance,  and  is 
easily  obtained  by  pouring  nitric  acid  upon  pieces  of  copper 
contained  in  a  glass  retort. 
The  arrangement  shown  in  the 
figure  is  very  convenient  for 
the  purpose.  Into  the  glass 
vessel-  a  put  some  clean  pieces 
of  metallic  copper,  and  then 
introduce  the  cover,  through 
which  passes  the  glass  tube  b, 
with  a  funnel  at  top,  and  ex- 
tending nearly  to  the  bottom 
of  the  vessel,  and  a  lead  tube,  c,  bent  at  right  angles,  to  convey 
away  the  gas  as  it  is  formed.  The  cover  must  fit  very  accurately, 
in  order  to  prevent  the  escape  of  the  gas,  which  is  rapidly  formed 
as  soon  as  a  little  nitric  acid  is  introduced  by  the  funnel  and 
tube  b.  It  may  be  collected  over  water,  but  a  small  proportion 
is  absorbed. 

The  changes  which  take  place  between  the  copper  and  the  acid 
are  indicated  as  follows  : — 

4  N05  +  3  Cu-=  3  (CuO,N05)  +  N02. 


Preparation  of  Nitric  Acid 


QUESTIONS. — 217.  How  is  the  binoxide  of  nitrogen  prepared? 
are  the  chemical  changes  that  take  place  ? 

17* 


What 


198 


COMPOUNDS   OS1   NITROGEN   AND   OXYGEN. 


Thus,  from  4  atoms  of  nitric  acid  and  3  of  copper,  there  are 
formed  3  atoms  of  nitrate  of  protoxide  of  copper,  and  one  of  the 
binoxide  of  nitrogen. 

218.  Binoxide  of  nitrogen  is  a  colorless  gas,  of  a  density  of 
1*039,  100  cubic  inches  weighing  a  little  more  than  32  grs.  Its 
most  striking  property  is  its  strong  affinity 
for  oxygen,  although  most  substances  intro- 
duced into  it  in  a  state  of  combustion  are 
extinguished.  Charcoal  and  phosphorus, 
however,  if  well  ignited,  burn  in  it  with 
great  splendor,  though  the  latter  by  careful 
heating  may  be  melted  in  it  without  igni- 
tion. When  allowed  to  escape  into  the 
air,  it  forms,  with  the  oxygen  of  the  air, 
dense  orange  fumes  of  nitrous  acid.  Thus, 
if  a  bell-glass  receiver,  filled  with  it  over 
water,  be  suddenly  inverted  in  the  air,  the 
dense  orange  fumes  of  nitrous  acid  formed 
by  its  union  with  the  oxygen  of  the  atmo- 
sphere will  rise  for  a  few  moments  from  its  interior,  like  smoke 
from  a  chimney. 

Let  a  receiver  filled  with  this  gas  be  placed  in  a  basin  of  pure 
water,  as  shown  in  the  figure;  and  then 
let  a  few  bubbles  of  oxygen  gas  be  forced 
in  by  a  pipe  leading  from  a  gasometer,  or 
by  means  of  a  gas-bag.  As  the  oxygen 
mixes  with  the  gas  within,  nitrous  acid 
fumes  are  produced,  which  are  immediately 
absorbed  by  the  water,  giving  it  a  slight 
acidity,  as  may  be  determiiied  by  the  usual 
tests.  By  continuing  to  force  in  the 
oxygen  gradually,  and  supplying  the  basin  with  water,  all 


Experiment  -with  Nitric 
Oxide. 


Nitric  Oxide  and  Oxygen. 


gas  will    at   length  disappear, 
water  as  nitrous  acid. 


being  entirely  absorbed  by  the 


QUESTIONS. — 218.  Describe  binoxide  of  nitrogen.  What  is  produced 
when  it  comes  in  contact  with  atmospheric  air  or  oxygen?  Describe  the 
experiment  with  a  receiver  filled  with  the  gas  over  water  and  oxygen  gas. 


COMPOUNDS   OP   NITROGEN   AND   OXYGEN.  199 

Binoxide  of  nitrogen  may  be  analyzed  in  the  same  manner  as  the 
protoxide  (216),  by  heating  in  a  small  quantity  of  it,  accurately  mea- 
sured, a  small  piece  of  potassium  or  sodium,  which  absorbs  the  oxygen, 
leaving  the  nitrogen  free,  the  volume  of  which  will  be  found  just  one- 
half  of  that  of  the  compound  gas.  The  binoxide  therefore  is  composed  of 

1  vol.  of  nitrogen,  which  weighs  0-972 

1  «       oxygen,  "  *        1-106 

2  "      binoxide,  "  2-078 

The  weight  of  1   vol.  or  the   density  is  therefore,  as   above   stated, 
2 -078 -4- 2  =  1-039. 

219.  Hyponitrous  Acid  — N03;  eq.,  (14  +  24=)  38.— This 
acid  is  formed  by  mixing  4  measures  of  binoxide  of  nitrogen  with 
1  of  oxygen,  both  perfectly  dry,  and  subjecting  the  mixture  to  a 
cold  at  least  as  low  as  zero.     It  is  a  colorless  liquid,  which  is  at 
once  decomposed  by  water  into  nitric  acid  and  the  binoxide.     This 
acid  does  not  combine  directly  with  bases,  but  its  salts  may  be 
formed  by  heating  carefully  the  corresponding  nitrates.     Thus  by 
heating  nitrate  of  potassa,  a  part  of  the  oxygen  of  the  nitric  acid 
is  expelled,  and  the  nitrate  is  converted  chiefly  into  hyponitrifce 
of  potassa,  as  indicated  in  the  following  formula : 

KO,N05  =  KO,N03  +  20. 

The  heat  should  be  carefully  applied,  and  the  process  arrested, 
as  soon  as  the  oxygen  which  comes  over  begins  to  be  mixed  with 
nitrogen  By  treating  the  mass  after  cooling  with  strong  alcohol 
the  hyponitrite  is  dissolved  out,  and  may  be  obtained  very  pure. 

220.  Nitrous  Acid— £J04;   eq.,  (14  +  32  =)  46.— Tnis  sub- 
stance is  formed,  as  we  have  seen,  whenever  binoxide  of  nitrogen 
comes  in  contact  with  oxygen.      It  may  also,  be  prepared  by 
heating  "dry  nitrate  of  lead  in  a  retort,  and  passing  the  vapor 
formed  through  a  tube  surrounded  with  a  freezing  mixture  to 
condense  it.     A  piece  of  apparatus  like  that  represented  in  the 

QUESTIONS. — What  is  the  effect  when  a  piece  of  potassium  is  heated 
in  a  tube  containing  nitric  oxide  ?  What  is  the  volume  of  nitrogen  that  is 
left?  219.  What  is  hyponitrous  acid?  Does  it  combine  directly  with 
bases?  How  may  the  hyponitrites  be  formed  ?  220.  How  may  nitrous 
acid  be  formed  ? 


200 


COMPOUNDS   OP   NITROGEN   AND   OXYGEN. 


figure  answers  the  purpose  well.  It  is  to  be  placed  in  a  proper 
vessel,  containing  the  freezing  mixture,  and 
connected  with  the  mouth  of  the  retort. 

As  thus  obtained,  this  acid  has  a  density 
of  142,  and  at  60°  F.  is  of  an  orange 
color,  but  becomes  yellow  when  cooled  to 
32°,  and  is  nearly  colorless  at  zero.  Though 
it  requires  a  temperature  nearly  as  low  as  zero  to  condense  it  to 
the  liquid  form,  the  liquid  boils  at  82°.  It  does  not  combine 
with  bases,  but  forms  compounds  with  some  of  the  stronger  acids 
It  is  decomposed  by  contact  with  water. 

221.  Nitric  Acid— N05;  eq.,  (14  +  40  =)  54.—  Nitric  acid, 
or  aquafortis,  is  usually  seen  as  a  liquid,  and  is  best  obtained  by 

decomposing  nitrate 
of  potash  or  nitrate 
of  soda  by  strong 
sulphuric  acid,  by 
the  aid  of  heat.  The 
salt,  previously  well 
dried,  is  placed  in  a 
retort  of  hard  glass, 
A,  with  an  equal 
weight  of  strong  sul- 
phuric acid,  in  a  fur- 
.nace,  and  surrounded 


Preparation  of  Nitri^  Acid. 


at  the  bottom  with  sand.  A  moderate  heat  is  applied,  and  the 
nitric  acid,  as  it  is  separated,  distils  over  into  the  receiver,  B, 
where  it  is  condensed.  To  render  the  condensation  more  com- 
plete, the  receiver  may  be  surrounded  with  a  net-work,  and  cold 
water  from  a  pipe,  i,  made  to  fall  constantly  upon  it.  The  water 
escapes  by  the  troughs  C  C  and  ed.  A  furnace  is  not  absolutely 
necessary;  the  heat  of  a  lamp  is  sufficient  in  all  laboratory 
j  operations. 

Nitric  acid,  as  thus  formed,  is  a  dense  liquid,  of  a  yellow  or 
orange  color,  and  always  contains  more  or  less  nitrous  acid  mixed 

QUESTIONS. — May  nitrous  acid  be  obtained  in  the  liquid  form  ?  Does 
it  combine  with  bases?  221.  How  is  nitric  acid  obtained ?  What  is  the 
common  or  commercial  name  of  this  acid  ?  Describe  nitric  acid. 


COMPOUNDS   OF   NITROGEN   AND   OXYGEN.  201 

with  it.  In  its  most  condensed  state  it  has  a  density  of  1-52,  and 
boils  at  188° ;  its  composition  being  then  N05,HO.  There  is 
another  definite  compound  of  the  acid  and  water,  N05,4HO, 
which  has  a  specific  gravity  of  142,  and  boils  at  253°.  The  first 
contains  14  per  cent,  of  water,  and  the  latter  40  per  cent. 

By  decomposing  dry  nitrate  of  silver*by  dry  chlorine,  nitrio 
acid  may  be  obtained  as  a  white  crystaline  solid,  which  is  readily 
soluble  in  water,  forming  the  common  aquafortis. 

Strong  nitric  acid,  when  exposed  to  the  atmosphere,  emits  dense, 
white  fumes,  which  are  exceedingly  suffocating.  Mixed  suddenly 
with  water,  it  occasions  a  considerable  rise  of  temperature ;  but 
mixed  with  snow,  it  produces  cold  by  the  rapid  liquefaction  which 
is  occasioned. 

Nitric  acid  may  be  frozen  by  cold.  The  temperature  at  which 
congelation  takes  place  varies  with  the  strength  of  the  acid.  The 
strongest  acid  freezes  at  about  58°  below  zero.  When  diluted 
with  half  its  weight  of  water,  it  becomes  solid  at  — 1^°.  By  the 
addition  of  a  little  more  water,  its  freezing  point  is  lowered 
to— 45°. 

It  is  one  of  the  most  energetic  acids  known,  and  oxydizes  many 
substances  powerfully.  Powdered  charcoal  and  oil  of  turpentine 
are  ignited  by  it,  and  most  animal  and  vegetable  bodies  disor- 
ganized. Phosphorus  is  oxydized  so  rapidly  as  to  produce  an 
explosion.  A  small  drop  on  the  skin  will,  in  a  few  seconds, 
destroy  its  vitality,  and  produce  a  permanent  yellow  spot.  There 
are  two  varieties  of  it  in  commerce,  called  single  and  double 
aquafortis,  the  latter  of  which  is  much  the  strongest,  and  usually 
is  of  a  deep  orange  color. 

222.  This  acid  is  sometimes  produced  by  the  union  of  the  oxygen  and 
nitrogen  of  the  atmosphere,  as  the  effect  of  lightnings,  and  is  found  as 
nitrate  of  ammonia  in  rain-water  after  a  shower  in  summer.  The  same 
effect  may  be  produced  by  the  electric  spark,  but  the  presence  of  water 
and  some  base  to  combine  immediately  with  the  acid  is  necessary.  Let 
a  tube  be  bent,  as  in  the  figure  on  next  page,  and  the  two  ends  covered 
with  metallic  cups,  one  of  them  opening  by  a  screw,  so  that  the  tube 
may  be  half" filled  with  a  weak  solution  of  potash.  Now  insert  the  screw 

QUESTIONS. — Does  nitric  acid  always  contain  water  when  in  the  liquid 
form  ?  How  may  it  be  obtained  in  the  solid  form  ?  May  aquafortis  be 
frozen?  What  is  said  of  its  oxydizing  power?  222.  How  may  nitrio 
acid  be  formed  by  the  direct  union  of  its  elements  ? 


202 


COMPOUNDS   OF   NITROGEN  AND   HYDROGEN. 


Nitric  Acid  Produced. 


and  divide  the  solution  into  two  equal  parts, 
as  nearly  as  may  be,  and  connect  it  with  the 
prime  conductor  of  an  electrical  machine, 
and  cause  a  succession  of  sparks  to  pass 
through  the  portion  of  air  contained  in  the 
central  part  of  the  tube.  Upon  examina- 
tion, the  solution  will  now  be  found  to  con- 
f  tain  nitrate  of  potassa;  the  nitric  acid  of 

•which  has  been  formed  by  the  union  of  the  constituent  gases  of  the 

atmosphere,  as  above  explained. 

223,  Gold-leaf  answers  well,  in  most  cases,  as  a  test  for  nitric 
acid.  The  substance  supposed  to  contain  it  is  mixed  with  a 
little  hydrochloric  acid,  and  the  mixture,  if  nitric  acid  is  really 
present,  should  then  be  capable  of  dissolving  the  leaf.  If  it  is 
a  salt  that  is  to  be  tested,  it  should  first  be  dissolved  in  water, 
and  the  solution  treated  in  the  same  manner  with  hydrochloric 
acid  and. gold-leaf. 

Nitric  acid  is  much  used  in  the  arts  for  etching  on  copper,  as  a 
solvent  for  the  metals,  &c.,  and  as  a  tonic  in  medicine.  In  the 
laboratory  of  the  chemist,  it  is  in  constant  and  most  important 
use  in  a  great  variety  of  operations. 


Compounds  of  Nitrogen  and  Hydrogen. 

224.  Ammonia— NH^  eq.,  (14  +  3  =  )  17.  —  This  gaseous 
substance  is  the  only  compound  of  nitrogen  and  hydrogen  that 

is  known.  It  has  been 
called  by  a  variety  of 
names,  as  hartshorn, 
spirits  of  hartshorn, 
volatile  alkali,  &c.  It 
has  sometimes  been  de- 
tected in  rain-water, 
either  alone  or  in  com- 
bination with  nitric  acid 
Collection  of  Ammonia.  (222) ;  but  it  is  readily 


QUESTIONS. — 223.  What  test  of  free  nitric  acid  is  mentioned  ?    224.  What 
is  the  composition  of  ammonia  ?     By  what  names  is  it  known  ? 


COMPOUNDS  OF  NITROGEN  AND  HYDROGEN.          203 

obtained  by  heating  the  common  solution  of  ammonia,  called 
aqua  ammonise,  or  a  mixture  of  sal  ammonia  and  recently  slaked 
linie.  When  the  latter  substances  are  mixed  the  odor  of  ammonia 
is  at  once  perceived,  but  it  is  evolved  freely  when  the  mixture  is 
moderately  heated.  It  is  rapidly  absorbed  by  water,  and  should 
therefore  be  collected  over  mercury.  The  reaction  is  as  follows : 

NH3,HC1  +  CaO  =  Ca,  Cl  +  HO  +  NH3. 

The  two  gases  do  not  combine  directly,  but  their  union  often 
takes  place  when  they  are  presented  to  each  other  in  their  nascent 
state  (226),  in  various  chemical  operations.  Thus,  during  the 
rusting  of  iron,  when  moisture  is  present  a  portion  of  ammonia  is 
frequently  produced,  and  when  zinc  is  dissolved  in  dilute  nitric 
acid  the  solution  will  usually  be  found  to  contain  a  little  nitrate 
of  ammonia. 

Ammonia  is  also  produced  during  the  destructive  distillation 
of  animal  substances ;  and  the  name  hartshorn  came  into  use 
from  the  circumstance  that  deer's  horns  were  made  use  of  for 
the  purpose. 

225.  Ammonia  is  a  colorless  gas,  and  possesses  a  very  pungent 
odor,  by  which  it  may  always  be  distinguished.  By  a  pressure 
of  six  or  seven  atmospheres  it  is  compressed  into  a  liquid ;  it  also 
takes  the  liquid  form  by  the  application  of  intense  cold,  under  the 
ordinary  atmospheric  pressure.  A  lighted  candle  plunged  into  it 
is  extinguished,  but  a  small  jet  of  it  burns  in  oxygen  gas.  Its 
density  is  about  0-59,  100  cubic  inches  weighing  18-29  grs. 

Ammonia  is  composed  of  one  volume  of  nitrogen  and  three 
volumes  of  hydrogen,  condensed  into  two  volumes. 

1  vol.  of  nitrogen  weighs  0-972  . 
3       "      hydrogen     "      0-207 

2  "      ammonia      "      1-179 

One-half  of  this,  or  0-589,  is  the  weight  of  one  volume,  or  the 
theoretical  density  of  the  gas. 

QUESTIONS. — How  may  ammonia  be  obtained  from  aqua  ammonia? 
What  is  said  of  its  absorption  by  water  ?  What  is  said  of  the  formation 
of  ammonia  during  the  rusting  of  iron?  225.  What  are  some  of  the 
properties  of  ammonia  ? 


<504  COMPOUNDS   OF   NITROGEN   AND    HYDROGEN. 

Thie  gas  is  largely  absorbed  by  water,  which  at  32°  is  capable 
of  dissolving  500  or  600  times  its  own  volume  of  it,  and  then 
forms  the  liquid  ammonia,  or  aqua  ammonias  of  commerce. 
As  the  gas  is  absorbed,  the  water  increases  considerably  in. 
volume,  so  that,  when  saturated,  its  density  is  only  0-87,  and  it 
contains  32  per  cent,  of  the  gas.  • 

Liquid  ammonia  is  be"st  prepared  by  the  use  of  a  Woulf's 
apparatus,  which  is  constructed  as  follows.  First  a  vessel  of 


Preparation  of  Aqua  Ammonia. 

glass  or  metal,  A.,  containing  the  substances  from  which  the  gas 
is  to  be  evolved,  is  placed  upon  a  furnace  or  other  source  of  heat, 
and  connected  by  a  tube  with  a  series  of  three-necked  bottles, 
B,  C,  D,  &c.,  each  partly  filled  with  water.  The  first  tube  from 
the  vessel  containing  the  materials,  it  will  be  observed,  terminates 
below  the  surface  of  the  water,  in  the  bottle  B,  so  that  the  gas 
coming  through  it  is  made  to  rise  through  the  water;  but  the  tube 
connecting  this  with  the  next  bottle  C  terminates  in  B  near  the 
top,  but  extends  downward  beneath  the  -surface  of  the  water  in  C. 
The  same  thing  will  also  be  observed  of  the  tubes  connecting 
together  the  other  bottles.  Now  when  the  gaseous  ammonia  is 
evolved  it  passes  over,  and  rising  through  the  water  in  C,  is 
absorbed,  but  any  other  gas  passes  on  in  like  manner  to  the  next 
bottle,  and  so  on  until  it  escapes  in  the  air.  If  any  of  the  am- 
monia escapes  from  the  first  bottle,  as  will  be  the  case  after  the 
water  has  become  in  part  saturated,  it  will  be  likely  to  be  con- 

QUESTIONS — What  is  said  of  the  absorption  of  ammonia  by  water? 
Describe  the  mode  of  preparing  the  liquid  ammonia. 


COMPOUNDS   OP   NITROGEN   AND   HYDROGEN.  205 

densed  in  the  next,  or  farther  on  in  the  series.  In  the  centre 
of  each  bottle  is  a  tube,  open  at  both  ends,  but  extending  down- 
ward so  as  to  terminate  below  the  surface  of  the  liquid.  It  ia 
designed  merely  as  a  safety  tube ;  it  is  plain  that  if,  in  using  the 
apparatus,  any  obstruction  occurs  in  one  of  the  tubes,  the  effect 
•will  be  to  force  out  the  liquid  through  these  central  tubes  without 
danger  to  the  apparatus ;  so  also  any  external  pressure  will  at  once 
be  equalized  by  the  entrance  of  the  air  through  these  tubes.  This 
apparatus  is  used  for  many  similar  purposes. 

In  order  to  ensure  the  full  saturation  of  the  water  in  the  bottles 
they  must  be  kept  cold  by  means  of  ice. 

Ammonia  has  all  the  properties  of  an  alkali  in  a  very  marked 
manner.  Thus  it  has  an  acrid  taste,  and  gives  a  brown  stain  to 
turmeric  paper;  though  the  yellow  color  soon  reappears  on  ex- 
posure to  the  air,  owing  to  the  volatility  of  the  alkali.  It  com- 
bines also  with  acids,  and  neutralizes  their  properties  completely. 

This  substance  is  used  extensively  in  the  laboratory  of  the 
chemist,  and  in  medicine.  Solution  of  ammonia,  taken  inter- 
nally in  considerable  quantity,  has  been  known  to  produce  death ; 
and  the  gas,  if  inspired  too  long,  is  apt  to  occasion  inflammation 
in  the  throat  and  lungs. 

226.  Nascent  State. — This  phrase,  which  occurs  above,  is  used  to  indi- 
cate the  state  of  a  body  as  it  is  evolved  from  a  compound  containing  it. 
In  the  case  alluded  to,  the  rusting  of  iron  in  the  presence  of  moisture, 
the  oxygen  which  unites  with  the  iron  is  mostly  supplied  by  the  water ; 
and  the  hydrogen,  as  it  is  thus  set  free,  is  said  to  be  in  its  nascent  state, 
and  just  at  the  moment  is  capable  of  combining  with  the  nitrogen  of  the 
air  to  form  ammonia,  which  it  will  not  do  under  other  circumstances. 
Many  other  substances,  when  thus  separated  from  compounds  of  which 
they  form  a  part,  manifest  a  disposition  to  form  compounds  with  bodies 
with  which  they  will  not  combine  directly. 

QUESTIONS. — What  is  the  design  of  the  central  tube  in  each  bottle? 
What  is  said  of  the  alkaline  properties  of  ammonia?  226.  What  is 
meant  by  the  nascent  state  of  a  body  ?  What  is  said  of  the  properties 
possessed  by  substances  in  this  state  ? 


18 


206  CHLORINE. 


GROUP  II. 

CHLORINE  "|  Electro-negative  elements,  which  constitute  a  very  distinct 
IODINE  !  natural  family.  Each  forms  a  single  acid  compound  with 
BROMINE  |  hydrogen ;  and  all  combine  with  the  metals,  forming  com- 
FLUORINE  j  pounds  that  are  similar. 

CHLORINE. 

Symbol,  01;  Equivalent,  354;  Density,  2.44. 

227.  History, — Chlorine  was  discovered  by  Scheele,  in  1774, 
and  for  many  years  was  regarded  as  a  compound,  but  its  true 
character,  as  a  simple  element,  is  now  universally  admitted.     It 
is  not  found  uncombined  in  nature,  but  is  abundant  in  its  com- 
pounds, especially  common  salt,  which  is  so  generally  distributed 
over  the  surface  of  the  earth.     It  receives  its  name  from  the 
Greek  chloros,  green,  because  of  its  yellowish-green  color. 

228.  Preparation, — Chlorine  gas  is  easily  prepared  by  pouring 
strong  hydrcchloric  acid  upon  half  its  weight  of  peroxide  of  man- 
ganese, in  a  glass  retort,  and  applying  a  gentle  heat.     It  may  be 
collected  over  hot  water,  but  not  without  some  being  absorbed  by 
it.     It  should  always  be  collected  in  bottles  with  good  stoppers, 
in  which  it  may  be  kept  for  some  time.     The  following  formula 
indicates  the  changes  that  take  place  : — 

Mn02  +  2HC1  =  MnCl  +  2110  +  Cl. 

A  cheaper  process,  and  nearly  as  convenient,  is  to  mix,  inti- 
mately, three  parts  of  common  salt  with  one  of  the  peroxide,  and 
pour  over  it  two  parts  of  sulphuric  acid,  previously  diluted  with 
an  equal  weight  of  water.  In  this  case, 

Mn02  +  NaCl  +  2S03  =  MnO,SO,  +  NaO,S03  +  01. 

QUESTIONS. — What  are  the  substances  of  the  second  group  ?  What  is 
said  of  them  as  a  group  ?  227.  What  facts  are  mentioned  in  the  history 
of  chlorine?  From  what  is  the  name  derived?  228.  Describe  the 
method  first  mentioned  for  preparing  chlorine.  Why  should  hot  water 
be  used  in  collecting  it  ?  Describe  the  mode  of  preparing  it  by  the  uso 
of  common  salt.  What  are  the  chemical  changes  that  take  place  ? 


CHLORINE. 


207 


The  chlorine  by  this 
process  is  evidently  sup- 
plied by  the  salt  (chlo- 
ride of  sodium)  and 
there  are  formed  sul- 
phate of  the  protoxide 
of  manganese  and  sul- 
phate of  soda. 

1 
*     It  is  afforded  also  by 

various  other  prepara- 
tions. 


Preparation  of  Chlorine 


229.  Properties, — Chlorine  is  a  dense  gas,  of  a  yellowish 
green  color,  as  above  stated,  and  has  an  astringent  taste,  and 
rather  disagreeable  odor.  The  weight  of  100  cubic  inches  is 
76  grains,  which  gives  a  density  of  244.  By  moderate  pressure 
it  is  converted  into  a  liquid,  which  has  a  density  of  about  1-33. 
As  cold  water  absorbs  the  gas  readily  it  cannot  be  collected  over 
it  without  great  loss; 
but,  in  consequence  of 
its  great  specific  gravity, 
it  may  be  collected  in 
an  open  vessel,  by  di- 
rect displacement  of  the 
*ir.  Let  a  be  the  flask 
containing  the  mate- 
rials, and  c  a  receiver 
in  which  the  gas  is  to 
be  collected,  the  tube 
from  the  flask  extend- 
ing nearly  to  the  bot- 
lom.  The  chlorine  gas 
being  so  much  heavier  than  air,  fills  up  the  receiver  just  as 
water  would  if  conveyed  into  it  in  the  same  manner;  and  if  the 
process  is  expeditiously  conducted,  the  chlorine  may  be  collected 
nearly  pure. 


Collection  of  Chlorine  by  Displacement  of  the  Air. 


QUESTIONS. — 229.  Describe  the-  properties  of  chlorine.     How  may  it 
be  collected  by  displacement  of  the  air? 


208 


CHLORINE. 


Prepared  by  either  of  the  modes  described  above  the  gas  is 
always  mixed  with  watery  vapor,  from  which  it  is  readily  separated 
by  passing  it  through  a  tube  containing  lumps  of  dry  chloride 
of  calcium.  After  being  evolved  from  the  materials  used  it 
should  be  made  to  pass  through  a  bottle  containing  a  small 
quantity  of  water,  to  separate  any  hydrochloric  acid  that  mai 


Preparation  of  Dry  Chlorine. 

have  come  over,  and  then  through  the  chloride  of  calcium  tube, 
which  will  absorb  all  the  watery  vapor;  it  may  then  be  collected 
in  a  bottle  by  displacement  of  the  air,  as  just 
described.  The  bottle  should  be  provided  with 
a  well-ground  glass  stopper. 

Chlorine  is  allied  to  oxygen  in  many  of  its 
properties;  alighted  candle  continues  to  burn 
in  it  for  a  time  with'a  dull  red  flame,  giving  off 
a  dense  black  smoke   of  uncombined  carbon  ; 
and  phosphorus  takes  fire  in  it  spontaneously, 
burning  with   great  brilliancy.      Some   of  the 
r       vj?w          metals  also,  if  in  thin  leaf  or  fine  powder,  take 
supports  combustion,  fire  in   it  spontaneously.     For  this  purpose,  a 


QUESTIONS. — How  may  the  gas  be  obtained  free  from  moisture  ?     Will 
chlorine  support  combustion?     How  is  phosphorus  affected  by  it? 


CHLORINE. 


209 


cwonne. 


tall  jar  should  be  used,  as  represented  in 
the  figure  on  the  left;  and  the  bottom 
should  be  covered  with  sand,  to  prevent 
the  breaking  of  the  glass  by  the  heated 
chloride  falling  upon  it.  It  has  a  strong 
affinity  for  hydrogen,  and  a  mixture  of 
the  gases  explodes  by  the  approach  of 
flame,  and  by  the  electric  spark,  precisely 
as  a  mixture  of  oxygen  and  hydrogen. 
If  a  piece  of  paper,  moistened  with  oil  of 
turpentine,  be  suspended  in  a  bottle  of 
chlorine,  it  takes  fire  spontaneously,  by 
the  chlorine  combining  with  the  hydrogen 
turpentine;  at  the  same  time  the 


Turpentine  In- 
flamed. 


carbon  of  the  turpentine  is  liberated,  in  a  state  of  minute  division, 
as  a  dense  black  smoke.  The  bottle  containing  the  chlorine 
should  have  a  large  mouth. 

One  of  the  most  important  properties  of  chlorine  is  its  bleaching 
power,  all  vegetable  and  animal  coloring  matters  being  speedily 
destroyed  by  it.  Powdered  indigo,  slightly  moistened  and  dropped 
into  a  bottle  containing  it,  even  if  it  is  considerably  diluted  with 
air,  soon  loses  its  color  entirely  ;  and  pieces  of  calico,  of  different 
colors,  suspended  in  it,  are  affected  in  the  same  manner,  without, 
in  the  least,  injuring  the  texture  of  the  cloth.  It  is  therefore 
much  used  in  preparing  rags  for  the  manufacture  of  writing- 
paper,  and  also  in  bleaching  cotton  and  linen  goods.  Writing 
done  with  common  ink  is  easily  removed  by  it;  but  printers'  ink, 
being  an  oily  preparation,  is  not  attacked  by  it. 

Chlorine  is  also  a  powerful  disinfecting  agent,  removing  at  once 
all  offensive  effluvia  from  sewers,  vaults,  and  other  places  where 
they  may  have  collected.  For  this  purpose,  bleaching-powder  (to 
be  .described  hereafter)  is  moistened  with  water,  and  placed  in 
shallow  dishes  in  the  apartments  to  be  fumigated. 

The  aqueous  solution  of  chlorine  is  best  prepared  by  the  use 

QUESTIONS.  —  What  is  said  of  the  affinity  of  chlorine  for  hydrogen? 
What.  is  its  effect  upon  oil  of  turpentine?     What  occasions  the  dense 
black  smoke?     What  is  said  of  the  bleaching  properties  of  chlorine? 
What  is  said  of  it  as  a  disinfecting  agent? 
18* 


210  COMPOUNDS   OF   CHLORINE   AND   OXYGEN. 

of  a  Woulfe's  apparatus  (225).    The  solution  readily  dissolves  gold- 
leaf,  forming  trichloride  of  gold. 

If  one  of  the  bottles  is  kept  cold  by  means  of  ice,  a  crystaline 
solid  will  be  deposited,  which  is  a  compound  of  one  atom  of  chlo- 
rine and  ten  atoms  of  water. 

230.  By  dexterously  putting  some  of  these  crystals  in  a  glass  tut 
and  sealing  it   hermetically,  liquid  chlorine  may  be  obtained.     By 

slight  elevation  of  temperature  the  solid  melts 
•  and  the  water  and  chlorine  separate,  the  latter 
of  -which,    in   consequence    of    the   pressure, 
takes   the   liquifl   form.      While    sealing   the 
tube  the  end  containing  the  crystals  must  be 
Preparation  of  Liquid  Chlorine,  kept  cold  by  means  of  ice. 

The  aqueous  solution,  if  prepared  in  the  dark  and  kept  constantly 
from  the  action  of  light,  undergoes  no  change  (173),  but  if  once  exposed 
for  a  few  moments  only  to  the  sun's  rays,  decomposition  of  the  water 
commences,  hydrochloric  acid  is  formed,  and  oxygen  set  free. 

The  proper  test  of  chlorine,  either  free  or  in  combination,  is  solution 
of  nitrate  of  silver ;  silver  and  chlorine  always  forming  a  dense  white  pre- 
cipitate,  quite  insoluble  in  water,  but  readily  soluble  in  aqua  ainmoniae. 


Compounds  of  Chlorine  and  Oxygen 

231.  The  compounds  of  chlorine  and  oxygen  are  five  in  number, 
as  follows,  viz. :— C10,C103JC104,C105,  and  C107,  all  of  which  are 
acids ;  but  as  the  affinities  of  these  substances  for  each  other  are 
very  feeble,  their  compounds  are  all  decomposed  by  slight  causes. 

232.  Hypochlorous  Acid  — CIO;    eq.,  (35-4-f8=)  43-4.— This  is  a 
gaseous  substance,  of  a  yellowish-green  color,  like  that  of  chlorine,  but 
a  shade   deeper.     It  exists  in  combination  with  lime  in  the   common 
bleaching-powder. 

233.  Chlorous  Acid— C103;  eq.,  (35-4  -f 24  =)  59-4—  Is  prepared  by 
the  action  of  oil  of  vitriol  upon  chlorate  of  potash. 

234.  Hypochloric  Acid— C104;   eq.,  (35-4  -f  32  =)  67-4.— This  com- 
pound is  also  gaseous,  and  of  a  deep  yellowish  'color.     It  is  formed  by 
the  action  of  sulphuric  acid  upon  chlorate  of  potash.     If  a  few  grains 

QUESTIONS. — How  is  the  aqueous  solution  of  chlorine  prepared  ?  May 
the  compound  of  chlorine  and  water  be  crystalized  ?  230.  How  may 
these  crystals  be  used  to  form  liquid  chlorine  ?  Can  the  aqueous  solu- 
tion be  long  preserved  without  decomposition?  What  test  for  chlorine 
is  mentioned  ?  231.  What  compounds  of  chlorine  and  oxygen  are  there? 
What  is  the  number  of  equivalents  of  oxygen  in  each  of  these  ? 


COMPOUNDS   OP   CHLORINE   AND   HYDROGEN.  211 

of  chlorate  of  potash  are  placed  in  a  wine-glass,  and  a  little  sulphuric 
acid  poured  in,  the  glass  will  be  soon  filled  with  the  gas,  which  will  be 
recognised  by  its  color.  If  now  a  rag,  wet  with  oil  of  turpentine,  be  pre- 
sented to  it,  on  the  end  of  a  wire  or  a  stick,  it  will  be  inflamed,  and  the 
gas  at  the  same  time  exploded. 

235.  Chloric  Acid— C105;  eqr,  (354  +  40  =)  754.— Chloric 
acid  is  obtained  by  passing  a  current  of  chlorine  through  a  strong 
solution  of  potash,  with  which  it  combines  as  it  is  formed,  pro- 
ducing  chlorate  of  potash.  At  the  same,  time  with  the  chlorate 
of  potash  there  is  also  produced  much  chloride  of  potassium ;  the 
reaction  takes  place  between  6  equivalents  of  chlorine  and  6  equiva- 
lents of  potash,  according  to  the  following  equation  : — 

6KO  +  6C1  =  5KC1  +  KO,C105.        % 

The  chlorate  being  only  slightly  soluble  in  water,  some  separates 
in  crystals  by  a  little  evaporation  of  the  water,  while  the  chloride 
remains  in  solution. 

To  obtain  the  acid  in  a  separate  state,  chlorate  of  baryta  is  first 
produced  and  then  decomposed  carefully  by  sulphuric  acid.  The 
BaO,S03  whicn  forms  is  separated  by  nitration,  and  the  chloric 
acid  obtained  as  a  syrupy  liquid.  It  is  decomposed  at  a  tem- 
perature of  104°. 

Perchloric  Acid  possesses  no  characters  that  render  it  of  any  special 
interest. 


Compounds  of  Chlorine  and  Hydrogen. 

236.  Hydrochloric  Acid— HC1;  eq.,  (354  +  1=)  364.— 
This  is  the  only  known  compound  of  chlorine  and  hydrogen ; 
and,  in  -solution  in  water,  has  long  been  used  in  the  arts,  under 
the  names  of  muriatic  acid,  and  spirit  of  salt.  It  is  formed  by 
the  action  of  diluted  sulphuric  acid  upon  common  salt.  The 
sulphuric  acid  should  be  diluted  with  about  an  equal  weight  of 

QUESTIONS. — 235.  How  is  chlorate  of  potassa  formed  ?  How  is  chloric 
acid  procured  from  this  salt?  236.  What  is  the  only  compound  of 
chlorine  and  hydrogen  that  is  known?  How  is  hydrochloric  acid 
prepared  ? 


212  COMPOUNDS   OP   CHLORINE   AND   HYDROGEN. 

water,  and  be  allowed  to  cool  before  being  used.     The  changes 
which  take  place  are  as  follows : — 

NaCl  +  S03>HO  =  NaO,S03  +  HC1. 

,From  this  it  appears  that  the  water  of  the  oil  of  vitriol  ia 
essential  to  the  process ;  it  is  decomposed,  yielding  its  oxygen  to 
the  sodium  to  form  soda,  which  combines  with  the  acid,  and  its 
hydrogen  to  the  chlorine  to  form  the  hydrochloric  acid. 

Abundant  fumes  of  the  gaseous  acid  will  be  given  off,  which 
should  in  no  case  be  allowed  to  diffuse  themselves  in  a  room 
where  there  are  articles  of  delicate  apparatus  made  of  metal, 
as  they  will  be  sure  to  be  corroded  after  a  little  time,  if  not 
immediately. 

It  is  also  formed  by  the  direct  union  of  its  elements.  When 
equal  measures  of  chlorine  and  hydrogen  are  mixed  together,  and 
an  electric  spark  is  passed  through  the  mixture,  instantaneous 
combination  takes  place,  heat  and  light  are  emitted,  and  hydro- 
chloric acid  is  generated.  A  similar  effect  is  produced  by  flame, 
by  a  red-hot  body,  and  by  spongy  platinum.  Light  also  causes 
them  to  unite.  A  mixture  of  the  two  gases  may  be  preserved, 
without  change,  in  a  dark  place;  but  if  exposed  to  the  diffused 
light  of  day,  gradual  combination  ensues,  which  is  completed  in 
the  course  of  twenty-four  hours.  The  direct  solar  ray,  like  flame 
and  the  electric  spark,  produces  an  explosion  by  a  sudden  inflam. 
mation  of  the  whole  mixture ;  but  to  insure  the  success  of  the 
experiment,  the  gases  should  be  very  pure,  and  the  chlorine 
recently  prepared  over  warm  water.  The  glass  vial  containing 
the  mixed  gases,  after  being  filled,  should  be  instantly  covered 
with  a  black  cloth,  which  can  be  suddenly  removed  by  a  stick,  or 
•  wire,  after  it  is  placed  in  the  sun's  rays. 

Hydrochloric  acid  is,  "of  course,  a  chloride  of  hydrogen.  When 
pure  it  is  a  colorless  gas,  of  which  100  cubic  inches  weigh  39-38 
grains,  giving  it  a  density  of  1-25.  By  strong  pressure  it  may 

QUESTIONS. — Explain  the  equation.  Is  the  presence  of  water  essential 
to  the  formation  of  hydrochloric  acid?  May  it  be  formed  by  the  direct 
union  of  its  elements  ?  What  several  means  are  mentioned  by  which  the 
gases  may  be  made  to  combine  ?  What  are  some  of  the  properties  of 
hydrochloric  acid  ? 


COMPOUNDS   OF   CHLORINE   AND   HYDROGEN.  213 

be  compressed  into  a  liquid.  It  is  quite  irrespirable,  and  in- 
capable of  supporting  combustion.  Water  absorbs  it  with  avidity, 
taking  up,  under  favorable  circumstances,  no  less  than  480  times 
its  own  volume.  During  the  absorption  it  increases  considerably 
in  volume,  and  the  saturated  solution  has  a  density  of  1/21,  and 
contains  about  forty-two  per  cent,  of  the  acid.  In  preparing  the 
liquid  hydrochloric  acid,  a  Woulfe's  apparatus  (225)  is  used,  only 
a  very  little  water  being  contained  in  the  first  bottle,  in  which 
most  of  the  impurities  mixed  with  the  gaseous  acid  will  be 
deposited.  In  the  open  air,  copious  fumes  of  the 
gas  constantly  arise  from  the  liquid,  which  produce 
a  cloud  of  smoke  if  any  ammonia  be  present  in 
the  air.  Thus,  let  a  little  aqua  ammonias  be 
poured  into  a  glass  vessel,  A,  with  a  large  mouth, 
and  then  invert  over  it  a  tumbler,  the  inside  of 
which  has  been  thoroughly  moistened  with  common 
hydrochloric  acid.  The  two  gases,  coming  in  con- 
tact, unite,  and  fill  both  glasses  with  a  dense,  white  Hydrochloric  Acid 

.  ' ,  and  Ammonia. 

smoke,  which  is  solid  hydrocnlorate  of  ammonia 
(159),  in  a  finely  divided  state.     The  same  thing  is  shown  when 
a  glass  rod  moistened  with  hydrochloric  acid  is  brought  near  an 
open  vessel  containing  aqua  ammonias. 

Gaseous  hydrochloric  acid  is  composed  of  equal  volumes  of  chlorine 
and  hydrogen  united  without  condensation. 

One  volume  of  chlorine  weighs  2 '440 

One         "        hydrogen    "  069 

Forming  two  vols.  hydrochloric  acid  2.509 
I 

The  weight  of  1  vol.,  or  the  theoretical  density  of  the  gas,  is  therefore 
^1|L9  =  1-254. 

237.  Aqua  regia,  so  called  because  of  its  ability  to  dissolve 
gold  and  platinum,  is  a  mixture  of  two  parts  of  hydrochloric  to 
one  of  nitric  acid.  •  Let  a  single  leaf  of  gold  be  placed  in  a  wine 

QUESTIONS. — What  is  said  of  the  absorption  of  hydrochloric  acid  by 
water  ?  What  is  said  of  the  fumes  produced  by  the  gas  -with  ammonia  ? 
What  is  said  of  the  volumes  of  chlorine  and  hydrogen  which  unite  to  form 
this  acid  ?  237.  What  is  aqua  regia  ?  Why  is  it  so  called  ? 


214  COMPOUNDS   OP   CHLORINE   AND   NITROGEN. 

glass  containing  a  little  hydrochloric  acid,  and  another  leaf  in  a 
separate  glass  with  some  nitric  acid ;  the  gold  will  remain  undis- 
solved  in  both  glasses  for  any  length  of  time ;  but,  on  mixing  the 
contents  of  the  glasses,  the  whole  of  the  gold  will  be  speedily  dis- 
solved. The  real  solvent  in  this  case  is  the  chlorine,  which  is 
liberated  by  the  action  of  the  acids  upon  each  other.  The  reaction 
is  shown  by  the  following  equation.  Thus, 

N05  +  2HC1  =  N03  +  2HO  +  01. 

This  decomposition,  however,  proceeds  only  so  far  as  to  saturate 
the  liquid  with  chlorine,  but  if  heat  is  applied  to  expel  the  chlorine, 
or  a  metal  placed  in  the  liquid  with  which  it  will  unite,  new  quan- 
tities of  the  acid  are  decomposed.  Nitrohydrochloric  acid,  there- 
fore, is  a  source  of  chlorine  in  a  very  concentrated  state,  and  is 
capable  of  dissolving  several  substances  which  are  not  attached 
by  any  single  acid. 

Hydrochloric  acid  may  readily  be  distinguished  by  its  odor  and 
volatility,  and  by  its  giving,  with  a  solution  of  nitrate  of  silver 
(230),  a  precipitate  of  the  white  chloride  of  silver,  which  is 
blackened  by  exposure  to  the  light. 

Liquid  hydrochloric  acid  is  extensively  used  for  various  pur- 
poses in  the  arts,  and  is  one  of  the  most  important  chemical 
agents  of  the  laboratory. 


Compounds  of  Chlorine  and  Nitrogen. 

238.  Terchloride  of  Nitrogen.— NC13 ;  eq.,  (14  -f  106-2  =) 
120-2. — There  is  known  only  a  single  compound  of  these  ele- 
ments, the  terchloride  of  nitrogen.  It  is  prepared  by  pass- 
ing a  current  of  chlorine  through  a  solution  of  the  hydrochlorate, 
or  other  salt  of  ammonia,  and  takes  the  form  of  a  dense  yellow 
liquid,  which  is  seen  in  small  globules  at  the  bottom  of  the  solu 
tion.  The  reaction  is  expressed  in  the  following  equation  : — 

NHS,HC1  +  6C1  =  4HC1  +  NC13. 

QUESTIONS. — What  compound  of  gold  is  formed?  How  may  hydro- 
chloric acid  be  known  ?  238.  What  compound  of  chlorine  and  nitrogen 
is  there?  What  is  said  of  it?  Explain  the  equation. 

I 


IODINE.  215 

The  liquid  has  a  density  of  1-65,  and  may  be  distilled  under  a 
pressure  less  than  one  atmosphere,  but  at  212°  it  explodes  with 
the  utmost  violence.  So  also  it  detonates  violently  by  the  mere 
contact  with  phosphorus,  many  of  the  oils,  &c.,  *and  never  should 
be  handled  but  with  the  greatest  care. 


IODINE. 

Kymbol,  I;  Equivalent,  127;  Density,  4-95 

239.  History. — Iodine  from  (iodes,  violet  color)  was  discovered 
in  the  ashes  of  sea-plants,  from  which  it  is  still  prepared,  by  M. 
Courtois  of  Paris,  in  the  year  1812.     It  is  found  also  in  certain 
ores  of  silver  and  zinc,  in  sea-water,  and  in  the  water  of  certain 
mineral  springs. 

240.  Preparation, — As  stated  above,  the  iodine  of  commerce 
is  obtained  from  the  ashes  of  sea-plants,  especially  the  fucus 


Preparation  of  Iodine. 

palmatus.     The  ley  obtained  by  lixiviating  the  ashes  is  first 
evaporated,  to  separate  a  portion  of  the  carbonate  of  soda  and 

QUESTIONS.— 239.  When  was  iodine  discovered  ?     In  what  is  it  found  t 
240.  What  is  the  mode  of  preparing  iodine  from  the  ashes  of  sea-plants  T 


216  IODINE. 

other  saline  compounds  it  contains,  which  are  less  soluble  than 
the  iodine  compounds — chiefly  the  iodides  of  sodium  and  magne- 
sium— and  are  therefore  first  to  crystalize  out  from  the  solution ; 
the  residue  is  then  mixed  with  peroxide  of  manganese  and  sul- 
phuric acid,  and  a  gentle  heat  applied,  when  the  iodine  distils 
over,  as  a  beautiful  violet-colored  vapor,  into  a  receiver  prepared 
for  the  purpose,  where  it  is  condensed.  A  simple  apparatus  like 
that  represented  in  the  figure  on  the  preceding  page  answers  well 
for  the  distillation. 

A  good  method  to  show  the  evolution  of  iodine,  is  to  heat  in  a 
glass  globe,  over  a  lamp  or  ignited  charcoal,  a  small  quantity  of 
sulphuric  acid,  and  throw  suddenly  into  it  25  or  30  grains  of  iodide 
of  potassium.  A  large  quantity  of  iodine  will  instantly  be  set 
free,  and  its  vapor  fill  the  globe. 

241.  Properties. — Iodine,  at  ordinary  temperatures,  is  a  soft, 
friable,  nearly  black  solid.  Usually  it  is  in  small  shining  crys- 
tals, which  have  a  metallic  lustre,  and  a  density  of  4-95.  Heated 
a  little  above  212°,  it  melts,  and  is  then  converted  into  a  beau- 
tiful violet- colored  vapor,  which  has  a  density  of  8-70  (air  being 
1),  and  100  cubic  inches  weigh  270-1  grains.  Iodine  is  a  non- 
conductor of  electricity  and  heat,  and  is  allied  to  oxygen  and 
chlorine  in  many  of  its  properties.  Its  odor  resembles  that  of 
chlorine,  but  is  less  offensive.  It  is  sparingly  soluble  in  water, 
requiring  about  7000  times  its  own  weight  of  this  liquid  for  com- 
plete solution  j  but  alcohol  and  ether  dissolve  it  freely,  forming  a 
deep  brown  solution.  A  few  of  the  crystals  pressed  upon  the 
skin  produce  a  deep  stain,  which  however  soon  disappears. 

Starch  affords  a  delicate  test  of  iodine,  forming  with  it  a  beau- 
tiful blue.  The  starch  should  be  prepared  by  dissolving  it  in  hot 
water,  and  allowing  it  to  cool  before  using.  Let  a  little  hot  water 
be  poured  upon  ashes  obtained  by  burning  a  piece  of  sponge,  and, 
after  filtering,  add  a  drop  or  two  of  solution  of  starch ;  then  pour 
in  a  few  drops  of  sulphuric  or  nitric  acid,  and  stir  it  gently, 
and  almost  always  the  blue  color  will  be  observed,  indicating  the 
presence  of  iodine. 

QUESTIONS. — 241.  Describe  the  properties  of  iodine.  What  is  %aiO 
of  its  solubility  in  vrater?  In  alcohol  and  sther?  What  test  of  iculin* 
is  mentioned  ?  How  may  iodine  be  detected  in  sponge  ? 


COMPOUNDS  OF  IODINE  AND  OXYGEN,  HYDROGEN,  ETC.    217 

Iodine  has  not  been  much  used  in  the  arts,  but  is  largely  em- 
ployed in  medicine.  In  the  Daguerreotype  process  (76),  it  is 
essential ;  and  recently  it  is  said  to  have  been  employed  in  dyeing. 


Compounds  of  Iodine  and  Oxygen,  Hydrogen,  &c. 

242.  Iodine  and  oxygen   combine  in  three  proportions,  pro- 
ducing iodous  I04,  iodic  I05,  and  periodic  I07,  acids ;  neither  of 
which  however  possesses  any  special  interest. 

243.  Hydriodic  Acid,  HI,  (iodide  of  hydrogen,)  is  a  gaseous 
substance,  of  a  specific  gravity  4-39,  and  in  many  of  its  properties 
strongly  resembles  the  corresponding  chloride  of  hydrogen  (hydro- 
chloric acid).     It  is  absorbed  by  water,  and  then  forms  the  liquid 
hydriodic  acid. 

It  is  best  prepared  by  placing  in 
a  glass  tube  alternate  layers  of  iodine, 
powdered  glass  (to  prevent  too  rapid 
action)  and  posphorus,  slightly  mois- 
tened with  water.  Iodide  of  phos- 
phorus is  first  formed,  which  is 
decomposed  by  the  water,  producing 

•i        j  L    j  •    j-         •?  Preparation  of  Hydriodic  Acid. 

phosphorous  acid  and  hydriodic  acid, 

the  last  of  which  being  gaseous  makes  its  escape,  and  may  be 
collected  in  a  dry  bottle  by  displacement  of  the  air,  or  it  may  be 
condensed  in  water. 

244.  Teriodide  of  Nitrogen— NI3.— From  the  weak  affinity  that  exists 
between  iodine  and  nitrogen,  these  substances  cannot  be  made  to  unite 
directly.     But  when  iodine  is  put  into  a  solution  of  ammonia,  the  alkali 
is  decomposed ;  its  elements  unite  with  different  portions  of  iodine,  and 
thus  cause  the  formation  of  hydriodic  acid  and  teriodide  of  nitrogen. 
The  latter  subsides  in  the  form  of  a  dark  powder,  which  is  characterized, 
like  chloride  of  nitrogen,  by  its  explosive  property.     It  often  detonates 
spontaneously  as  soon  as  it  is  dry,  and  even  when  moist,  by  the  slightest 
causes.     Heat  and  light  are  emitted  during  the  explosion,  and  iodine  and 
nitrogen  are  set  free,  the  former  of  which  may  be  seen  at  the  instant  in 
the  form  of  vapor. 

QUESTIONS. — What  use  is  made  of  iodine?     242.  What  compounds 
of  iodine  and  oxygen  are  mentioned?     243.  Describe  hydriodic  acid 
How  is  it  formed  ?     244.  Describe  teriodide  of  nitrogen. 
19 


218  BROMINE. 

Chlorine  combines  "with  iodine  when  made  to  pass  over  it  in  a  dry 
glass  tube,  or  when  passed  through  water  in  which  crystals  of  iodine  are 
diffused.  The  two  substances  form  several  different  compounds,  but  they 
are  not  at  present  well  understood.  One  of  these,  probably  the  proto- 
chloride,  Id,  has  been  used  in  the  Daguerreotype  process. 


BROMINE. 
Symbol,  Br;  Equivalent,  80;  Density,  2-97. 

245.  History. — Bromine  was  discovered  in  1826,  in  sea-water; 
and  received  its  name,  bromine  (from  bromos,  offensive  odor),  in 
consequence  of  its  exceedingly  disagreeable  smell.  Kecently  it 
has  been  obtained  in  large  quantities  from  the  waters  of  some 
of  the  salt-springs  in  Pennsylvania  and  Virginia. 

.  246.  Preparation. — The  usual  mode  of  preparing  bromine  is  a 
little  complex.  First,  the  brine  from  the  spring  is  evaporated, 
and  the  common  salt  removed  by  crystalization,  then  the  mother- 
liquor,  or  bittern,  as  the  uncrystalizable  residue  is  called,  is  treated 
with  a  current  of  chlorine  to  decompose  the  bromides  of  magne- 
sium, sodium,  &c.,  and  sulphuric  ether  afterwards  added,  by  which 
the  bromine  that  has  been  separated  from  its  compounds  by  the 
chlorine  is  taken  up,  and  rises  to  the  surface  as  a  solution  of 
bromine  in  ether. 

Another  method  is  to  mix  with  the  solution  sulphuric  acid  and 
peroxide  of  manganese,  as  in  the  preparation  of  iodine ;  and  then 
distilling  with  a  gentle  heat.  The  same  apparatus  (240)  may  be 
used  as  in  the  preparation  of  iodine,  but  the  receiver  must  be 
kept  cool  by  a  current  of  cold  water. 

247.  Properties. — Bromine  is  a  liquid  of  a  blackish-red  color, 
and  specific  gravity  2-97.  At  a  temperature  a  little  below  zero 
it  is  frozen,  and  boils  at  about  117°,  forming  a  vapor  of  a  beau- 
tiful blood-red  color,  and  specific  gravity  5-39,  air  being  1.  It 

QUESTIONS. — What  is  said  of  the  compounds  of  chloride  and  nitrogen  ? 

245.  When  was  bromine  discovered  ?     From  what  is  the  name  derived  ? 

246.  From  what  is  it  obtained?      What  is  the  mode  of  preparing  it  ? 

247.  Describe  its  properties. 


COMPOUNDS  OF  BROMINE,  WITH  OXYGEN,  ETC.     219 

stains  the  skin  yellow,  like  iodine,  but  less  intensely.  Vapor 
of  bromine  ignites  phosphorus  spontaneously,  and  a  lighted 
candle  burns  in  it  a  short  time. 

Bromine,  in  many  of  its  properties  is  closely  allied  to  chlorine 
and  iodine.  Taken  into  the  system  it  is  highly  poisonous,  and  its 
vapor  possesses  considerable  bleaching  power.  With  starch  it 
forms  a  yellow  color. 

Like  chlorine,  it  forms  a  compound  with  water,  which  crys 
talizes  when  exposed  to  the  cold  of  a  freezing  mixture  of  salt  and 
snow.  The  compound  is  Br,10HO. 

Bromine  is  sometimes  used  in  medicine,  and  much  more 
extensively  in  photography,  especially  in  the  Daguerreotype 
process. 


Compounds  of  Bromine,  with  Oxygen,  Hydrogen^  &c. 

248.  Bromic  Acid,  Br05,  is  the  only  well  determined  com- 
pound of  bromine  and  oxygen.  It  is  a  liquid,  and  may  be  pro- 
cured of  the  consistency  of  syrup.  It  is  very  corrosive,  and  sour 
to  the  taste,  and  by  a  temperature  of  212°  is  decomposed. 

249  Hydrobromic  Acid,  HBr,  is  a  colorless  gas  of  a  density 
2-73.     To  prepare  it,  a  tube  of  the  form  of  the  letter  W  is  pro- 
vided, and  the  part  at  the  left 
filled  with  pieces  of  phosphorus 
mixed  with  pounded  glass,  and 
the  whole  moistened  with  water. 
Into  the  end  at  the  right  some 
bromine  is  then  poured,  and  a 
cork  firmly  inserted;  and  into     "  preparation  of  Hydrobromic  Acid.        * 
the  other-  end  a  smaller  tube  is 

fixed,  by  means  of  a  perforated  cork,  to  convey  away  the  hydro- 
bromic  acid  as  it  is  formed.  The  whole  being  ready,  a  gentle 
heat  is  applied  to  the  part  containing  the  bromine;  and  the  vapor 
as  it  is  formed,  attacking  the  phosphorus,  first  produces  bromide 

QUESTIONS.— What  other  elements  does  bromine  resemble?  Does  it 
combine  with  water?  What  use  is  made  of  it?  248.  Describe  bromio 
»cid.  249.  Describe  hydrobromic  acid,  and  the  mode  of  preparing  it 


220  FLUORINE. 

of  phosphorus,  which  is  at  once  decomposed  by  the  water,  forming 
phosphorous  and  hydrobromic  acids,  the  latter  of  which,  being 
gaseous,  passes  off,  and  may  be  collected  over  mercury. 

The  gas  is  rapidly  absorbed  by  water,  like  hydrochloric  acid, 
and  the  concentrated  solution  gives  off  fumes  in  the  air.  In 
most  of  its  properties  it  closely  resembles  hydrochloric  acid. 

By  intense  cold  and  pressure  the  gas  may  be  condensed  to  the 
liquid  form. 

250.  Hydrobromic  acid  is  composed  of  equal  volumes  of  vapor  of  bro- 
mine and  hydrogen  combined  -without  condensation.  Thus, 

1  vol.  vapor  of  bromine  weighs  5-390 
1    "          "         hydrogen     "  069 


2  vols.  hydrobromic  acid,  5-459 

One  volume  of  the  acid  therefore  weighs  2-729. 


FLUORINE. 
Symbol,  F;  Equivalent,  19;  Density,  1-29. 

251.  History  and  Properties. — Fluorine  has  long  been  known 
to  exist,  but  it  has  not,  until  recently,  been  obtained  in  a  separate 
state.  It  is  found  in  nature  in  considerable  abundance  in  the 
mineral  called  fluor  spar,  which  is  a  compound  of  this  substance 
with  calcium,  the  metallic  base  of  lime.  It  is  a  brownish-colored 
gas,  of  specific  gravity 'about  1-29  (probably),  and  bleaches  like 
chlorine. 

Such  is  its  affinity  for  other  substances  that  it  attacks  them 
with  violence,  even  gold  and  platinum ;  and  can  be  prepared  and 
kept  only  in  vessels  made  of  fluor  spar,  which,  being  already 
saturated  with  the  substance,  is  not  acted  on  by  it. 

QUESTIONS. — What  is  said  of  the  absorption  of  hydrobromic  acid  by 
water?  250.  Considered  as  gaseous,  what  is  its  composition  ?  251.  Give 
the  history  and  properties  of  fluorine.  What  is  said  of  its  affinity  for 
other  substances  ?  Of  what  only  can  vessels  be  made  to  contain  it  ? 
Why  ig  not  this  substance  acted  on  by  it  ? 


COMPOUNDS     OF     FLUORINE.  221 


Compounds  of  Fluorine. 

Fluorine  seems  to  be  incapable  of  uniting  with  oxygen,  but 
combines  with  hydrogen,  forming  the  acid  compound  HF. 

252.  Hydrofluoric  Acid—  HF;  pq.,  (19  +  1=)  20.—  This  acid 

is  formed  by  subjecting  powdered  fluor  spar,  moistened  with  strong 
sulphuric  acid,  to  a  very  gentle  heat  in  a  leaden  vessel.  The  acid 
distils  over  as  a  pungent,  corrosive,  vapor,  but  may  be  condensed 
in  a  leaden  receiver,  that  is  kept  surrounded  with  ice.  The 
reactions  are  as  follows  :  — 


CaF  +  S03,HO  =  CaO,S03  +  HF. 

As  thus  formed,  the  acid  has  a  density  of  1-07,  and  manifests 
a  strong  affinity  for  water,  with  which  it  combines  with  great 
energy.  It  attacks  glass  powerfully,  combining  with  its  silica, 
and  may  therefore  be  used  to  etch  it.  This  is  done  by  spreading  a 
thin  coat  of  bees'-wax  or  varnish  upon  the  glass,  and  tracing  the 
design  upon  it,  taking  care  to  cut  quite  through  the  wax.  The 
liquid  acid  is  now  poured  over  the  coated  surface,  or  it  is  exposed 
a  few  minutes  to  the  acid  vapor,  and  the  wax  afterwards  removed  ; 
the  design  will  then  be  found  beautifully  traced  upon  the  glass. 

This  acid  attacks  animal  substances  powerfully,  and,  therefore, 
should  always  be  handled  with  great  care. 

Fluorine  unites  also  with  chlorine,  iodine,  bromine,  and  some  others 
of  the  elements,  but  the  compounds  are  not  important. 

QUESTIONS.  —  Does  fluorine  combine  with  oxygen  ?  252.  Describe  tho 
mode  of  preparing  hydrofluoric  acid.  Describe  its  properties.  How  may 
it  be  used  for  etching  upon  glass  ?  What  is  said  of  its  action  upon  ani- 
mal substances  ?  Does  fluorine  combine  with  chlorine,  iodine,  &o.  ? 

19* 


-22  SULPHUR. 


GBOUP  IIL 

SULPHUR  )  Elements  in  many  of  their  properties  closely  resembling 
SELENIUM  >  each  other,  and  forming  similar  acid  compounds  with 
TELLURIUM  J  oxygen  and  hydrogen. 


SULPHUR. 
Symbol,  S;  Equivalent,  16;  Density,  1-99. 

253.  History  and  Preparation. — Sulphur,  called  also  brim- 
stone, has  been  known  from  the  remotest  antiquity.  It  occurs,  as 
a  mineral  production,  in  many  parts  of  the  world,  particularly  in 
volcanic  regions,  as  in  the  neighborhood  of  Naples,  in  some  of  the 
Sandwich  Islands,  and  in  the  island  of  Sicily.  In  combination 
with  several  of  the  metals,  as  iron,  lead,  copper,  &c.,  it  is  still 
more  abundant,  and  is  found  in  almost  every  place.  From  one 
of  its  compounds  with  iron,  called  iron  pyrites,  it  is  procured  in 
large  quantities,  for  the  purposes  of  commerce.  It  is  found,  also, 
in  many  organic  bodies,  as  in  eggs,  in  the  hair,  horns,  and  hoofs 
of  animals,  and  in  the  seeds  of  black  mustard. 

The  island  of  Sicily  furnishes  a  large  part  of  all  sulphur  of 
commerce ;  the  native  sulphur  here  occurs  in  immense  beds  mixed 
more  or  less  with  gypsum,  lime,  and  other  earthy  matter.  This 
sulphurous  earth  is  first  heated  in  pots  so  as  to  melt  the  sulphur, 
which  is  dipped  out  with  ladles,  the  earthy  matter  settling  to  the 
bottom.  The  sulphurous  earth  remaining  as  sediment  is  then 
heated  in  earthen  pots,  which  are  arranged  ia  double  rows,  and 
entirely  inclosed  in  mason-work,  except  at  the  top,  where  is  an 
opening  by  which  they  are  charged  and  emptied.  At  the  sides, 
in  the  open  air,  pots  are  arranged  to  receive  the  sublimed  sulphur, 
which,  taking  the  liquid  form,  passes  finally  into  buckets  situated 
as  shown  in  the  figure  on  next  page. 

QUESTIONS. — AY  hat  elements  constitute  group  3d  of  the  metalloids'? 
253.  Give  the  history  of  sulphur.  "With  what  is  it  found  combined?  In 
what  erganic  bodies  is  it  contained?  Describe  the  mode  of  separating  it 
from  the  earthy  matter  with  which  it  is  mixed. 


SULPHUR 


223 


Separation  of  Sulphur. 

The  figure  represents  a  section  of  the  rnason-work  with  two  of 
the  included  pots,  and  also  the  external  receivers  with  which  they 
are  connected,  and  the  buckets. 

254.  Properties. — Sulphur  is  a  brittle  solid,  of  a  greenish- 
yellow  color,  emits  a  peculiar  odor  when  rubbed,  and  has  little 
*taste.  It  is  a  rion-conductor  of  electricity,  and  is  excited  nega- 
tively by  friction.  It  fuses  at  226°,  and  becomes  nearly  as  liquid 
as  water;  but  if  the  heat  be  raised  as  high  as  430°,  it  becomes 
so  tenacious  that  the  vessel  containing  it  may  be  inverted  without 
spilling  it,  and  is  then  of  a  dark  molasses  color.  When  heated 
to  at  least  428°,  and  then  poured  into  water,  it  becomes  a  ductile 
mass,  which  may  be  used  for  taking  the  impressions  of  seals. 
After  some  time,  it  changes  into  its  ordinary  state. 

Fused  sulphur  has  a  tendency  to  crystalize  in  cooling.  A  crys- 
taline  arrangement  is  perceptible  in  the  centre  of  common  roll 
sulphur;  and,  by  good  management,  regular 
crystals  may  be  obtained.  For  this  purpose, 
several  pounds  of  sulphur  should  be  melted  in 
an  earthen  crucible  ;  and,  when  partially  cooled, 
the  outer  solid  crust  should  be  pierced,  and  the 
crucible  quickly  inverted,  so  that  the  inner  and 
as  yet  fluid  .parts  may  gradually  flow  out.  On  SulPbur 
breaking  the  solid  mass,  when  quite  cold,  a  confused  arrangement 
of  prismatic  crystals  will  be  found  in  the  interior. 

Sulphur  is  dimorphous  (184) ;  that  is,  it  is  capable  of  cryt- 
talizing  in  two  distinct  primary  forms,  the  oblique  rhombic 

QUESTIONS. — 254.  Describe  the  properties  of  sulphur.  How  may  it  b« 
crystalized  ?  Why  is  it  said  to  be  dimorphous  ? 


224  SULPHUR. 

prism,  and  the  rhombic  octahedron-,    the  first  belonging  to  the 
monoclinic,  and  the  second  to  the  trimetric  system. 

Sulphur  is  very  volatile,  and  begins  to  rise  in  vapor  even  before 
it  is  completely  fused.  At  about  750°,  it  boils,  and  the  vapor, 
if  in  a  close  vessel,  will  be  condensed  on  any  cold  surface,  forming 
fhefloicers  of  sulphur.  The  density  of  its  vapor  is  about  6-65. 
"When  vapor  of  sulphur  is  brought  in  contact  with  vapor  of  alco- 
hol, they  unite ;  but  solid  sulphur  is  quite  insoluble  in  alcohol,  or 
water,  but  dissolves  in  boiling  oil  of  turpentine,  and  in  sulphide 
of  carbon. 

By  melting  the  flowers  of  sulphur  and  pouring  it  into  moulds, 
the  roll-sulphur  of  commerce  is  formed.  In  this  form  it  is  very 
brittle,  and  will  sometimes  break  by  the  heatf  of  the  hand.  It  is 
the  only  substance  known  that  always  becomes  negatively  excited 
by  friction,  whatever  may  be  the  nature  of  the  substance  used  as 
the  rubber.  -,J* 

The  vapor  of  sulphur  combines  readily  with  iron  and  other 

metals,  attended  with  all  the  pher 
nomena  of  combustion.  Let  the 
breech  of  a  gun-barrel  be  heated  to 
redness,  and  a  lump  of  sulphur 
dropped  into  it,  and  then  let  the 
muzzle  be  instantly  closed  by  a 
cork ;  a  jet  of  vapor  of  sulphur  will 
issue  violently  from  the  touch-hole, 
r  4  which  will  be  inflamed  as  it  enters 

Iron  Wire  and  Vapor  of  Sulphur.  ^  ^  .    ^  ft  buQch  Qf  ^j  .^ 

wire,  held  in  it,  will  burn  freely,  forming  sulphide  of  iron,  which 
will  fall  in  drops. 

The  sulphur  of  commerce  generally  has  an  acid  reaction,  pro- 
bably in  consequence  of  a  slight  oxidation  that  is  gradually 
taking  place.  Organic  substances  in  contact  with  sulphur  are 
always  more  or  less  acted  upon  by  the  acid  or  acids  thus  produced. 

QUESTIONS. — What  is  the  boiling  point  of  sulphur?  What  are  the 
flowers  of  sulphur  ?  Is  it  soluble  in  water  or  alcohol  ?  How  is  roll- 
Bulphur  formed  ?  What  is  said  of  its  electrical  state  when  rubbed  ?  How 
may  iron  wire  be  made  to  burn  in  vapor  of  sulphur  ?  Why  does  the  sul- 
phur of  commerce  usually  have  an  acid  reaction  ? 


COMPOUNDS   OF   SULPHUE   AND   OXYGEN.  225 

Uses  of  Sulphur. — Sulphur  is  used  extensively  in  the  arts,  and 
in  medicine.  It  is  employed  in  the  manufacture  of  gunpowder, 
sulphuric  acid,  the  different  kinds  of  matches,  vermillion,  &c.,  and 
for  taking  impressions  of  seals.  In  medicine,  it  is  used  in  cuta- 
neous diseases,  and  as  a  cathartic  and  alterative 


Compounds  of  Sulphur  and  Oxygen. 

255.  Sulphur  and  oxygen  form  as  many  as  seven  different  com- 
pounds, viz. : — 

1.  Hyposulpharous  acid S202. 

2.  Trisulpho-hyposulpliuric  acid S505. 

8.  Bisuipho-hyposuiphuric  acid S405. 

4 .  MonSsutpfib-fiy  posulphuric  acid S305. 

5.  Sulphurous  acid S02. 

\    6.  Hyp^iuTphfec  acid S205. 

7.  Sulphuric  acid S03. 

Of  these,  the  fifth  and  last  are  by  far  the  most  important ;  and 
only  these  will  be  here  described. 

256.  Sulphurous  Acid  —  S02;  eq.,  (16  +  16  =)  82.  — This 
substance  is  gaseous  at  ordinary  temperatures,  and  is  the  sole 
product  of  the  combustion  of  sulphur  in  the  open  air,  or  in  dry 
oxygen  gas.     It  is  more  conveniently  prepared,  however,  by  heat- 
ing strong  sulphuric  acid  in  contact  with  mercury  or  pieces  of 
copper.      One  equivalent  of  the  sulphuric  acid   gives  up  one 
equivalent  of  its  oxygen  to  unite  with  the  metal,  and  the  oxide 
thus  formed  is  immediately  dissolved  by  a  second  atom  of  the 
sulphuric  "acid,  while  the  sulphurous  acid  passes  off  as  a  gas.  .  Thus, 

Hg  +  2SO,  =  HgO,SO,+  S08. 

Another  very  easy  method  is  to  heat  in  a  retort  a  mixture  of  6 
parts  of  powdered  peroxide  .of  manganese  and  1  part  of  sulphur. 

QUESTIONS. — What  use  is  made  of  sulphur  in  the  arts  ?  255.  How 
many  compounds  of  sulphur  and  oxygen  are  mentioned  ?  256.  Describe 
sulphurous  acid,  and  the  mode  of  preparing  it.  . 


226 


COMPOUNDS   OF   SULPHUR   AND   OXYGEN. 


Preparation  of  Sulphurous  Acid. 


By  this  mode,  the  peroxide  gives  up  one-half  of  its  oxygen,  which 
unites  with  sulphur  to  form  the  sulphurous  acid,  and  protoxide 

of  manganese  remains  in 
the  retort. 

An  arrangement  like 
that  figured  in  the  mar- 
gin, answers  well  for  its 
preparation,  by  either 
mode.  As  the  gas  forms 
it  is  made  to  pass  through 
a  little  water,  to  condense 
any  vapor  of  sulphuric 
acid  that  may  have  come 
over,  and  it  may  then  be 
collected  over  mercury. 
Sulphurous  acid  is  a  dense,  colorless  gas,  100  cubic  inches  of 
which  weigh  68-55  grains,  giving  it  a  specific  gravity  of  2-24.  It 
is  distinguished  from  all  other  gases  by  its  suffocating  odor,  which 
every  one  has  recognized  in  burning  sulphur.  It  is  absorbed 
largely  by  water,  and  may  be  condensed  into  the  liquid  form  by 
moderate  pressure,  or  by  a  cold  of  zero.  A  little  of  the  liquid 

may  be  obtained  very  easily, 
by  putting  a  small  quantity  of 
mercury  and  sulphuric  acid  in 
a  bent  tube,  as  represented  in 
the  figure,  sealing  it  hermeti- 
cally, and  supplying  heat  to  the  extremity,  a,  which  contains  the 
materials,  while  the  other,  b,  is  kept  cool  by  means  of  ice,  or  the 
evaporation  of  ether.  The  liquid  will  be  soon  found  to  collect  in 
the  cool  part  of  the  tube.  Care  should  be  taken  not  to  heat  the 
tube  too  much,  lest  it  should  burst. 

A  better  method  to  procure  the  liquid  is  to  prepare  a  tube,  (as 
in  the  figure  on  next  page,)  by  closing  one  end,  and  drawing  out 
a  part  in  the  middle  to  a  capillary  bore,  and  then  inserting  it  in  a 
freezing  mixture  of  snow  and  salt.  If,  now,  a  current  of  the  gas, 
first  dried  by  passing  through  a  chloride  of  calcium  tube,  be  made 


Preparation  of  Sulphurous  Acid  in  Liquid 
Form. 


QUESTIONS. — What  is  said  of  the  odor  of  sulphurous  acid  ?     How  may 
it  be  obtained  in  the  liquid  form  ? 


COMPOUNDS    OF    SULPHUR  AND   OXYGEN.  227 

to  enter  the  open  end"  of  the  tube,  it  will  be  con- 
densed and  collected  in  the  lower  part.  When  this 
part  is  nearly  filled,  still  keeping  in  the  freezing  mix- 
ture, the  upper  part  may  be  separated  and  the  lower 
part,  hermetically  sealed,  and  the  liquid  preserved  for 
any  length  of  time.  Or  a  tube  like  that  represented 
in  the  figure  on  the  right 
margin  may  be  used.  The  bulb 
at  the  centre  part  is  to  be  sur- 
rounded with  a  freezing  mixture 

"PTfvnnrai'nn      » 

of  Liquid  sui-  *n  a  sultakk  vessel,  as  a  glass  Preparation  of  Liquid  Sui. 
phurous  Acid,  tumbler  j  and  when  a  sufficient  phurous  Acid, 
quantity  of  the  fluid  has  accumulated,  the  two  ends  of  the  tube 
may  be  hermetically  sealed  before  it  is  removed  from  its  place  in 
the  freezing  mixture.  Under  the  ordinary  atmospheric  pressure 
it  becomes  liquid  at  about  14°,  but  at  a  temperature  of  59°  it 
requires  a  pressure  of  about  2  atmospheres.  The  liquid  has  a 
density  of  142.  When  allowed  to  escape  in  the  open  air  it  eva- 
porates rapidly,  producing  a  cold  of  — 60°  to  — 76°,  according 
to  the  temperature  of  the  air  and  other  circumstances.  By  severe 
cold  it  may  be  frozen,  and  with  water  it  forms  a  compound 
(S029HO)  which  may  be  solidified. 

257.  Sulphurous  acid  is  composed  of  1  volume  of  oxygen  and  ^  of  a 
volume  of  vapor  of  sulphur,  condensed  into  1  volume.  If  we  burn  a 
small  quantity  of  sulphur  in  a  .glass  globe  over  mercury,  the  sulphur  is 
converted  into  sulphurous  acid,  but  after  cooling  the  volume  of  gases  is 
found  to  be  unchanged.  The  acid  therefore  occupies  the  same  space  as 
the  oxygen  entering  into  its  composition  Therefore  if  we  subtract  the 
weight  of  the  volume  of  oxygen  from  that  of  a  volume  of  sulphurous 
acid,  there  should  remain  ^  <ft  a  volume  of  vapor  of  sulphur.  '  This  ire 
find  to  be  the  case  very  nearly.  Thus, 

1  vol.  sulphurous  acid  weighs  2-247 
1'"    oxygen  (subtract)    "      1-106 

£    "    vapor  of  sulphur,  1-141 

QUESTIONS. — Describe  the  two  modes  mentioned  for  collecting  sul- 
phurous acid  in  glass  tubes.  At  what  temperature  does  it  become 
liquid  ?  What  is  the  density  of  liquid  sulphurous  acid  ?  What  is  said 
of  the  cold  produced  by  its  evaporation  ?  257.  What  is  the  composition 
of  one  volume  of  sulphurous  acid  ? 


228  COMPOUNDS   OP   SULPHUR   AND   OXYGEN. 

We  have  heretofore  (254)  taken  the  volume  of  sulphur  vapor  to  bo 
fi-654,  one-sixth  of  which  is  1-109.  The  discrepancy  in  the  results  is 
occasioned  by  the  great  difficulty  in  obtaining  accurately  the  real  weight 
of  the  volume  of  sulphur  vapor. 

288,  Sulphurous  acid  is  much  used  for  bleaching,  especially 
articles  of  straw ;  which,  in  a  moist  state,  are  suspended  in  an 
atmosphere  charged  with  the  gas.  For  this  purpose,  the  gas  is 
formed  by  burning  sulphur  in  the  air,  in  some  enclosure,  as  a  box 
or  empty  cask,  in  which  the  articles  to  be  bleached  are  suspended. 

259.  Sulphuric  Acid—  S03;  eq.,  (16  +  24  =)  40.— This  acid 
is  always  seen  as  a  dense  liquid,  not  unlike  oil  in  appearance ; 
and,  having  been  formerly  obtained  altogether  by  the  distillation 
of  green  vitriol  (sulphate  of  iron),  it  received  the  name,  oil  of 
vitriol,  by  which  it  is  now  often  known.     It  is  prepared  at  the 
present  time,  at  Nordhausen,  Germany,  by  the  same  mode.     Green 
vitriol  is  thoroughly  dried  by  heat,  and  then  distilled,  at  a  high 
temperature,  by  which  it  is  decomposed,  and  -the  acid  passes  over 
and  condenses  as  a  brown  oil-like  liquid,  which  still  contains  one 
eq.  of  water  for  every  two  eq.  of  the  acid.     Its  composition,  there- 
fore is  2S03,HO.     Its  density  is  1-9,  or  nearly  twice  that  of 
water.     When  this  liquid  is  again  distilled,  at  a  moderate  heat,  a 
dry,  silky  solid  is  obtained,  which  is  the  pure  compound,  S03; 
but  it  possesses  no  acid  properties '  until  water  is  added,  which 
changes  it  to  common  sulphuric  acid.     This  solid  has  a  strong 
affinity  for  water,  and  hisses  like  a  hot  iron  when  thrown  into  it. 

260.  The  common  method  of  preparing  the  oil  of  vitriol  of  com- 
merce is,  to  burn  a  mixture  of  sulphur  and  nitrate  of  potash, 
or  soda,- in  a  furnace  so  contrived  that  the  current  of  air  which 
supports  the  combustion  conducts   the  gaseous  products  into  a 
large  leaden  chamber,  the  bottom  of  which  is  covered  to  the 
depth  of  several   inches   with    water.      Numerous   complicated 
changes  take  place  in  the  leaden  chamber,  during  the  combustion 
of  the  sulphur,  by  which  the  oxygen  from  the  air  is  transferred 

QUESTIONS. — 258.  What  use  is  made  of  sulphurous  acid  ?  259.  Describe 
sulphuric  acid.  How  is  the  Nordhausen  acid  prepared  ?  How  may  the 
solid  acid  be  obtained  from  it?  What  is  the  composition  and  density 
of  the  Nordhausen  acid  ?  260.  What  is  the  mode  of  preparing  the  com- 
mon oil  of  vitriol  of  commerce  ? 


COMPOUNDS   OP  SULPHUR  AND   OXYGEN.  229 

to  the  sulphurous  acid  formed  by  the*  combustion  of  the  sulphur, 
converting  it  into  sulphuric  acid. 

la  the  first  place,  as  the  mixture  burns,  sulphurous  acid  is 
formed  (256),  and  binoxide  of  nitrogen  ;  —  the  latter  by  the 
decomposition  of  the  nitric  acid  of  the  salt;  —  and  the  two  gases 
with  a  current  of  air  are  carried  together  into  the  leaden  cham- 
ber,  the  binoxide  of  nitrogen,  N02,  at  the  same  time  absorbing 
oxygen,  and  being  thus  converted  (218)  into  nitrous  acid  (N04).  * 

Secondly,  these  two  gases,  in  the  absence  of  water,  are  capable 
of  combining  to  form  a  crystaline  solid,  the  composition  of  which 
is  N04,2S02,  and  which,  on  coming  in  contact  with  water,  is  at 
once  decomposed  into  binoxide  of  nitrogen  and  sulphuric  acid. 
Thus, 

^=  2S03  +  N02. 


Or,  more  properly, 

N04,2S02,  2HO  =  2(S03,HO)+  N02. 

Thirdly,  if  at  the  same  time  as  the  mixed  gases  from  the  com- 
bustion of  the  sulphur  enter  the  chamber,  steam  be  also  forced 
in,  the  crystals  just  alluded  to  are  not  formed,  but  all  the  reac- 
tions described  take  place*in  the  order  mentioned,  the  hydrated 
sulphuric  acid,  as  it  forms,  falling  like  rain  to  the  bottom  of  the 
chamber. 

The  binoxide  of  nitrogen,  being  set  free,  combines  again  with 
atmospheric  oxygen  present,  forming  nitrous  acid,  N04,  as  before, 
and  this,  with  the  sulphurous  acid,  by  the  reaction  of  water,  again 
producing  sulphuric  acid,  and  so  on  indefinitely. 

These  are  the  essential  reactions  that  take  place  in  the  process, 
but  they  are  often,  perhaps  always,  accompanied  by  others,  which 
however  tend  to  the  same  result,  viz.,  the  conversion  of  the  sul- 
phurous acid,  formed  from  the  burning  sulphur,  into  sulphuric 
acid. 


QUESTIONS. — Describe  the  reactions  .which  take  place.  Firstly? 
Secondly  ?  Thirdly  ?  Do  other  reactions  tending  to  the  same  result 
usually  accompany  the  above  ? 

20 


230  COMPOUNDS   OP   SULPHUR   AND   OXYGEN. 

Firstly,  a  portion  of  the  nitrous  acid,  N04,  in  the  leaden  cham- 
ber, when  but  little  moisture  is  present,  is  converted  into  mono- 
hydrated  nitric  acid,  and  hyponitrous  acid,  N03.  Thus, 

2N04  +  KO  =  N05,HO  +  N03. 

If  a  large  quantity  of  moisture  is  present,  the  nitrous  acid  is  con- 
verted into  hydrated  nitric  acid  and  binoxide  of  nitrogen.     Thus, 

6N04  +  nHO  =  4N05,nHO  +  2N02. 

Any  hyponitrous  acid,  N03,  that  may  have  been  formed,  as 
indicated  in  the  second  equation  above,  when  the  supply  of 
moisture  is  increased,  undergoes  a  similar  change,  producing 
nitric  acid  and  binoxide  of  nitrogen. 

Secondly,  sulphurous  acid,  S02,~  by  the  reaction  of  hydrated 
nitric  acid,  is  converted  into  hydrated  sulphuric  acid,  while  the 
nitric  acid,  N05,  by  the  loss  of  oxygen  is  changed  to  nitrous  acid, 
N04.  Thus, 


S02  +  N06  +  wHO  =  S03,nHO  +  N04. 

We  have,  then,  as  the  result,  sulphuric  and  nitrous  acids,  the 
former  of  which  mixes  with  the  water  at  the  bottom  of  the  cham- 
ber, while  the  latter,  remaining  in  ttie  gaseous  state,  is  ready 
again  to  go  through  the  same  reaction  as  before,  being  thus  made 
a  vehicle  for  conveying  oxygen  from  the  atmosphere  to  the  sul- 
phurous acid. 

In  some  manufactories,  no  nitrate  of  potash  is  used,  but  the 
sulphur  is  burned  alone,  and  nitric  acid,  in  proper  vessels,  is 
placed  in  the  leaden  chambers  in  such  a  situation  that  it  shall  be 
evaporated  by  the  heated  sulphurous  acid  and  other  gases  enter- 
ing from  the  furnace  ;  reactions  similar  to  those  above  take  place 
with  the  same  results. 

The  figure  following  will  serve  to  illustrate  the  process.  C  C  is 
a  section  of  the  chamber  lined  inside  with  sheet  lead,  and  sup- 
ported at  the  ends  by  mason-work.  At  A  is  the  furnace  for 

QUESTIONS.  —  Describe  the  other  reactions  tending  to  the  same  result 
which  accompany  those  already  mentioned. 


COMPOUNDS   OP   SULPHUR   AND   OXYGEN  231 


Manufacture  of  Sulphuric  Acid. 

burning  the  mixture  of  sulphur  and  nitric  salt,  the  fumes  of  which 
are  carried  directly  into  the  chamber,  now  filled  only  with  air, 
and  at  B  a  steam  boiler  from  which  steam  in  one  or  more  jets  is 
constantly  entering  the  chamber,  for  the  purposes  described  above. 
A  valve  at  the  the  top  allows  the  escape  of  the  spent  gases.  „ 

261,  For  a  class  experiment,  the  apparatus  figured  below  answers 
well  to  illustrate  the  mode  of  manufacturing  this  acid.     A  large 


Illustrates  the  Preparation  of  Oil  of  Vitriol. 


balloon   glass,  A,  is  provided,    containing  a  small  quantity  of 
water,  a  two-necked  flask,  B,  partly  filled  with  small  pieces  of 

QUESTIONS. — Describe  the  first  figure  on  this  page.  261.  Describe  the 
apparatus  figured  in  connection  with  this  paragraph.  What  is  illustrated 
by  it? 


232  COMPOUNDS   OP   SULPHUR   AND   OXYGEN. 

copper,  and  a  second  flask,  C,  containing  mercury  and  strong  oil 
of  vitriol.  These  two  flasks,  B  and  C,  are  connected  with  the 
balloon,  A,  by  means  of  tubes  inserted  in  perforated  corks,  as 
shown  in  the  figure ;  and  a  lamp  then  applied  to  C,  from  which 
sulphurous  acid  fumes  will  soon  be  made  to  pass  over  to  the  bal- 
loon, A.  Into  the  flask,  B,  some  nitric  acid,  a  little  diluted  with 
water  is  now  poured  by  the  long-necked  funnel,  which,  acting 
upon  the  copper  (217),  will  soon  supply  binoxide  of  nitrogen  to 
mix  with  the  other  gases  contained  in  A.  The  red  fumes  of 
nit'rous  acid  will  at  once  appear  in  A,  and  all  the  changes  take 
place  described  above,  resulting  in  the  production  of  a  small 
quantity  of  oil  of  vitriol.  Through  the  cork  in  the  mouth  of  thv1 
balloon  glass,  A,  two  glass  tubes  bent  at  right  angles  are  inserted, 
by  which  the  air  within  may  be  changed,  by  blowing  into  one 
of  them  by  the  mouth. 

.  In  the  manufacture  of  this  acid  on  a  large  scale,  the  acid,  as  it 
comes  from  the  leaden  chambers,  always  has  an  excess  of  water, 
its  density  varying  from  1-35  to  1-50.  It  is  then  heated  in 
leaden  pans  until  its  density  become's  about  1-75,  and,  finally,  in 
platinum  retorts,  by  which  all  excess  of  water  is  expelled,  and  its 
density  is  brought  to  1-84.  Its  boiling  point  is  then  617°,  and 
its  freezing  point  — 30°. 

Oil  of  vitriol,  we  thus  see,  always  contains  water;  the  most  con- 
centrated, that  of  Nordhausen,  as  stated  above,  containing  one 
atom  to  every  two  atoms  of  the  acid ;  or,  expresseddfcy  symbols, 
its  composition  is  2SQ3,HO.  As  prepared  by  the  ordinary  mode, 
it  contains  one  atom  of  acid  to  one  of  water,  or  its.  composition  is 
S03,HO.  If  to  about  49  parts  of  common  oil  of  vitriol  we  add 
9  parts  of  water,  we  have  an  acid  the  specific,  gravity  of  which 
will  be  about  1-78,  and  its  composition  S03,2HO.  It  will  then 
freeze  at  about  the  same  temperature  as  water,  but  on  the  applica- 
tion of  heat  the  solid  does  not  melt  until  the  temperature  rises 
to  45°. 

A  fourth  compound  of  water  and  sulphuric  acid  is  S03,3HO, 
which  has  a  specific  gravity  of  1-63.  It  boils  at  about  338°. 

QUESTIONS. — What  is  the  derfsity  of  the  acid  as  it  is  drawn  from  the 
leaden  chambers  ?  How  is  a  portion  of  the  water  expelled  ?  What  ia 
the  proportion  of  water  in  the  Nordhausen  acid  ?  In  common  oil  of 
vitriol  ?  Are  there  other  definite  compounds  of  this  acid  and  water  ? 


COMPOUNDS   Off  SULPHUR  AND   OXYGEN.  233 

Common  oil  of  vitriol  is  the  monohydrated  acid,  S03,HO. 
Exposed  to  the  open  air  it  rapidly  absorbs  moisture,  and  increases 
in  volume,  so  that  a  small  vessel  partly  filled  with  it,  if  left  open, 
is  often  found  running  over  after  a  few  days. 

Place  a  few  drops  of  it  in  a  watch  glass  in  the  pan  of  a  small 
balance,  and  exactly  counterpoise  it  by  weights  placed  in  the 
other  pan ;  in  a  very  few  moments  the  effect  of  the  absorption 
of  moisture  will  be  seen.  It  may  therefore  be  used  to  separate 
moisture  from  gases  which  are  not  acted  on  by  it,  by  passing  tfce 
gas  through  tubes  containing  pieces  of  pumice  stone  moistened 
with  the  acid. 

Sulphuric  acid  is,  perhaps,  the  most  important  of  all  the  acids, 
as  by  its  aid  nearly  all  the  others  are  produced.  Its  acid  pro- 
perties are  very  decided ;  aided  by  heat,  it  decom- 
poses animal  and  vegetable  substances,  causing  a 
deposition  of  charcoal,  and  formation  of  water, 
which  it  absorbs.  Its  affinity  for  water  is  very 
great,  and  the  combination  of  the  two  substances 
is  attended  with  the  production  of  considerable 
heat.  If  a  mixture  of  four  parts  of  the  acid  and  Mixt™of  S°3HO 

and  HO  produces 

one  of  water  is  stirred  with  a  test-tube  containing    Heat, 
sulphuric  ether,  the  heat  generated  will  be  sufficient  to  cause  the 
ether  to  boil. 

Free  sulphuric  acid  is  occasionally  found  in  the  water  of 
springs,  as  at  Byron,  Genesee  County,  New  York;  but  such 
cases  are  rare. 

Uses. — Sulphuric  acid  is  applied  in  the  arts,  and  in  the  labora- 
tory, to  very  many  important  uses ;  as,  in  the  preparation  of  the 
other  acids,  the  extraction  of  soda  from  common  salt,  the  manu- 
facture of  alum,  sulphate  of  iron,  chlorine,  &c.  It  is  also  used 
as  a  solvent  for  indigo,  and  in  the  various  manufactures  of  the 
metals. 

Test. — Chemists  possess  an  unerring  test  of  the  presence  of 
sulphuric  acid.  If  a  solution  of  chloride  of  barium  is  added  to  a 

QUESTIONS. — How  may  the  absorption  of  water  from  the  atmosphere 
by  oil  of  vitriol  be  shown  ?     What  is  said  of  the  affinity  of  this  acid  for 
water  ?     What  is  the  effect  when  it  is  mixed  with  water  ?     What  use  ia 
made  of  it  ?    What  test  of  its  soluble  salts  is  mentioned  ? 
20* 


234  COMPOUNDS   OF   SULPHUR   AND   HYDROGEN. 

liquid  containing  free  sulphuric  acid,  or  any  sulphate  in  solution,  t 
it  causes  a  white  precipitate,  sulphate  of  baryta,  which  is  charac- 
terized by  its  insolubility  in  acids  and  alkalies. 


Compounds  of  Sulphur  and  Hydrogen. 

262.  There  is  only  one  well-determined  compound  of  sulphur 
and  hydrogen,  the  /protosulphide,  or  hydrosulphuric  acid,  HS ; 
though  by  a  particular  process  a  second  compound  is  obtained,  as 
a  heavy,  yellowish  liquid,  which  is  supposed  to  be  a  bisulphide, 
HS2.     The  former  only  will  be  here  described. 

263.  Hydrosulphuric  Acid— HS ;  eq.,  (16  +  1=)  17.— Thb 
substance,  often  called  sulphuretted  hydrogen,  is  gaseous,  and  inaj 
easily  be  prepared  by  the  action  of  diluted  sulphuric  acid  upon 
powdered  protosulpbide  of  iron,  formed  by  intensely  heating  a 
bar  of  iron,  and  then  rubbing  it  with  a  roll  of  sulphur,  or  by 
heating  intensely  common  iron  pyrites  (native  bisulphide  of  iron) 
for  some  time  in  a  covered  crucible. 

One  mode  of  preparing  hydrogen,  it  will  be  recollected  (197, 
204),  is  by  the  action  of  dilute  oil  of  vitriol  upon  metallic  iron ; 
but  if  instead  of  iron  we  use  sulphide  of  iron,  a  particle  of  sulphur 
being  liberated  at  the  same  time  as  the  particle  of  hydrogen,  the 
two  combine,  and  gaseous  sulphide  of  hydrogen  is  evolved.  The 
reactions  are  as  follows : — 

FeS  +  S03,HO  =  FeO,S03  +  IIS. 

An  apparatus  like  that  represented  in  the  figure  on  the  next 
page  is  convenient  for  the  purpose.  The  sulphide  of  iron  is  first 
introduced,  and  after  the  cork  with  the  tubes  is  inserted,  the  acid 
is  added  by  means  of  the  long-necked  funnel. 

The  gas  may  also  be  prepared  by  the  action  of  hydrochloric 
acid  upon  native  sulphide  of  antimony  finely  pulverized,  aided 

QUESTIONS. — 262.  What  only  well-determined  compound  of  sulphur 
and  hydrogen  is  mentioned  ?  263.  How  is  it  prepared  ?  '  How  is  sul- 
phide of  iron  prepared  for  the  purpose?  Describe  the  reactions  that 
take  place. 


COMPOUNDS  OP   SULPHUR  AND   HYDROGEN. 


235 


Hydrosulphuric  Acid. 


f  by  a  gentle  heat.     The  reactions  then  are  as  expressed  in  the 
following  equation : — 

SbS  +  HC1  =  SbCl  +  HS. 

Hydrosulphuric  acid  is  a  colorless 
gas,  of  a  most  offensive  odor,  similar 
to  that  of  putrefying  eggs ;  100  cubic 
inches  of  it  weigh  36  93  grains,  giving 
it  a  density  of  1-191.  At  the  ordinary 
summer  temperature,  it  takes  the  liquid 
form  under  a  pressure  of  about  15  atmo- 
spheres, and  by  a  cold  of  — 122°  is 
frozen.  A  jet  of  it  burns  readily  in  the 
open  air,  forming  water  and  sulphurous 
acid. 

Cold  water  absorbs  2  or  3  times  its  own  volume  of  the  gas,  and 
acquires  its  peculiar  odor  and  taste;  but  the  gas  is  all  given  off 
again  when  the  water  is  boiled.  Water  impregnated  with  the 
gas,  if  kept  for  a  time,  becomes  milky  from  the  decomposition 
of  the  gas,  and  the  separation  of  the  sulphur  contained  in  it. 

Sulphur-springs,  which  occur  in  many  places  in  New  York, 
Virginia,  and  other  States,  .are  springs,  the  waters  of  which  are 
naturally  impregnated  with  hydrosulphuric  acid.  They  may 
always  be  recognised  by  the  offensive  odor,  which  extends  to  a 
distance  around  them,  and  by  their 
blackening  pieces  of  silver  coin,  by 
the  formation  of  sulphide  of  silver. 
Water,  possessing  all  the  properties 
of  that  of  the  most  noted  sulphur- 
springs,  may  be  prepared  artificially, 
by  passing  a  current  of  this  gas,  for  a 
few  minutes,  through  cold  water.  Let 
a  little  diluted  sulphuric  acid  be  poured  preParation  of  SulPhur  Water- 
upon  some  powdered  sulphide  of  iron,  in  a  small  bottle,  and  then 
insert  a  cork  with  a  beut  tube,  as  shown  in  the  figure,  the  other 

QUESTIONS. — What  are  some  of  the  properties  of  hydrosulphuric  acid? 
What  is  said  of  its  absorption  by  water  ?  What  are  sulphur  springs  f 
How  may  sulphur  water  be  prepared  artificially  ? 


236 


COMPOUNDS   OP   SULPHUR  AND   HYDROGEN. 


end  of  which  shall  dip  in  a  vial  of  cold  water.     After  the  gas  4 

has  bubbled  through  it  a  few  minutes,  it  will  be  found  fully 

impregnated. 

This  gas  blackens  many  colorless  metallic  salts,  by  the  forma- 

tion of  metallic  sulphides.  An  amusing  experiment  may  be 
performed  in  the  following  manner: 
Let  a  picture  be  traced  on  white 
paper  with  a  solution  of  sugar  of  lead, 
which  is  perfectly  colorless,  and  the 
picture,  at  a  little  distance,  will  be 
invisible.  Let  the  back  of  the  paper 
be  now  moistened  by  means  of  a  wet 
sponge  ;  and,  after  tacking  it  to  the 
wall,  let  a  current  of  this  gas  be 
directed  against  it,  and  all  the  parts 
traced  by  the  lead  solution  will  in- 
stantly become  dark  brown,  or  black, 

by  the  formation  of  sulphide  of  lead  on  the  paper. 

264.  The  composition  of  this  gas  is  easily  determined  by  heating  some 

tin-foil  in  a  measured  quan- 
tity of  the  gas.  Let  the  tube 
be  of  the  form  represented  in 
the  figure,  and  let  the  tin-foil 
be  placed  in  the  upper  part  by 
means  of  a  wire  after  the  gas, 
carefully  measured,  has  been 
introduced  ;  and  then  having 
the  open  end  of  the  tube  im- 
mersed in  mercury,  heat  the 
tin-foil  by  means  of  a  spirit- 
lamp.  All  the  sulphur  will 
be  immediately  absorbed  by 

the  metal,  and  there  will  remain  only  the  hydrogen,  which  will  however 

occupy  the  same  space  as  before.     Now, 

One  volume  of  hydrosulphuric  acid  gas  weighs  1-191 
One       '  "          hydrogen  (subtract)  -069 


Picture. 


Analysis  of  HS. 


There  remains  for  the  sulphur, 


1-122 


This  is  very  nearly  (162)  the  weight  of  one-sixth  of  a  volume  of  vapor  of 

QUESTIONS. — What  is  said  of  the  action  of  sulphur  water  upon  many 
colorless  metallic  salts  ?  264.  How  may  the  composition  of  hydrosul- 
phuric acid  be  determined  ? 


COMPOUNDS   OF   SULPHUR  AND   CHLORINE. 


237 


sulphur ;  so  the  composition  of  hydrosulphurio  acid  must  be  one  volume 
o?  hydrogen  and  one-sixth  of  a  volume  of  sulphur  vapor,  condensed  to 
one  volume. 


Compounds  of  Sulphur  and  Chlorine, 

265.  There  are,  it  is  believed,  several  compounds  of  these  two 
elements,  but  two  only  (or  perhaps,  three)  have  been  obtained  in 
a  separate  state,  the  dichloride,  S2C1,  and  the  chloride,  SCI. 

266.  Bichloride  of  Sulphur— S2C1  j  eq.,  (2  x  16  +  354=) 
67-4. — The  formation  of  this  compound  requires  an  apparatus 
which  is  somewhat  complex.     To  prepare  the  chlorine,  a  flask,  A, 
containing  some  peroxide  of  manganese,  is  provided,  a  tubulated 
retort,  D,  containing  a  quantity  of  sulphur,  and  a  three-necked 
bottle,  B,  for  the  purpose  of  washing  the  chlorine.     These  are 
connected  together  by  tubes,  as  shown  in  the  figure,  and  some 
hydrochloric  acid  poured  into  A  by  means  of  the  crooked  tube, 


Bichloride  of  Sulphur. 


the  design  of  which  is  to  prevent  any  escape  of  the  gas,  as  would 
be  the  case  if  the  liquid  was  poured  directly  in.      Everything 

QUESTIONS. — 265.   What  is   said   of  the   compounds  of  sulphur  and 
chlorine  ?     266.  How  is  dichloride  of  sulphur  formed  ? 


238  COMPOUNDS   OF   SULPHUR  AND   CHLOKINE. 

being  ready,  heat  is  applied  to  the  sulphur  in  D,  so  as  to  melt  it, 
and  also  a  gentle  heat  to  A,  to  cause  a  slow  evolution  of  chlorine. 
This  gas,  after  being  washed  in  B,  is  dried  by  passing  through  a 
chloride  of  calcium  tube  T,  and  finally  comes  in  contact  with  the 
vapor  of  sulphur  in  D,  where  the  compound  in  question  (S2C1) 
is  formed,  and  passes-  as  a  vapor  into  the  receiver,  E.  This  being 
kept  cool  by  a  stream  of  cold  water  from  the  vessel  F,  the  dichloride 
is  condensed,  and  any  atmospheric  air  or  other  gaseous  matter  passes 
off  by  the  waste-tube  inserted  in  E.  The  liquid  thus  obtained  must 
be  separated  from  a  little  sulphur  it  contains  by  a  second  distillation. 
Dichloride  of  sulphur  is  a  reddish-yellow  liquid,  having  a  dis- 
agreeable, and  very  peculiar  odor,  which  boils  at  about  280°.  Its 
specific  gravity  is  1-69,  and  that  of  its  vapor  4'668,  It  is  imme- 
diately decomposed  by  contact  with  water. 

Dichloride  of  sulphur,  considered  in  the  gaseous  state,  is  composed 
of  one  volume  of  chlorine,  and  one-third  of  a  volume  of  sulphur  vapor, 
condensed  into  one  volume.  Thus, 

One  volume  of  chlorine  weighs  2-440 

One-third  vol.  sulphur  vapor  weighs  6-^-4  2-218 


One  vol.  dichloride  (or  its  density),  4-658 

The  density  thus  obtained,  called  the  theoretical  density,  it  will  "be 
Been,  differs  but  slightly  from  that  given  above,  obtained  by  direct 
experiment. 

267.  Chloride  of  Sulphur— SCI ;  eq.,  (16  +  354  =)  51-4.— 
This  compound  is  prepared  by  passing  a  current  of  chlorine 
through  a  quantity  of  the  preceding,  until  it  is  entirely  saturated, 
and  then  distilling  at  a  temperature  of  147°.  -  It  is  a  deep  red 
fluid,  having  a  density  of  1-62. 

The  density  of  its  vapor  is  3-549.  Considered  in  the  gaseous  state,  it 
is  composed  of  one  volume  of  chlorine  and  one-sixth  of  a  volume  of  sul- 
phur vapor,  condensed  to  one  volume. 

One  volume  of  chlorine  weighs  2-440 

One-sixth  of  a  vol.  sulphur  vapor  weighs  1-109 


One  volume  of  chloride,  3-549 

>ounds  of  sulphur  with  nitro 
of  little  interest,  are  not  here  described. 


The  compounds  of  sulphur  with  nitrogen,  iodine  and  bromine,  being 


QUESTIONS. — Describe  the  properties  of  dichloride  of  sulphur.  267.  How 
is  chloride  of  sulphur  formed  ?     Describe  its  properties. 


SELENIUM.  239 

SELENIUM. 

Symbolj  Se;  Equivalent,  39-5;  Density,  4-32. 

\.  History,  etc, — Selenium  was  discovered,  in  1817,  by 
Berzelius,  and  received  its  name  from  selene,  the  moon.  It  is 
usually  found  associated  with  sulphur,  in  some  of  its  compounds 
with  other  substances,  especially  sulphide  of  iron  (iron  pyrites). 
It  is  found  also  in  combination  with  copper,  lead,  mercury,  silver, 
and  other  metals.  From  any  of  these  it  is  prepared  by  several 
different  processes. 

Selenium,  at  ordinary  temperatures,  is  a  solid  of  a  deep  brown 
color,  the  shade  varying  a  little,  according  as  it  is  seen  in  a 
powder  or  in  a  solid  mass.  When  melted  and  suddenly  cooled, 
it  has  a  vitreous  conchoidal  fracture,  and  becomes  negatively 
electrical  by  friction  in  very  dry  air.  When  heated  to  212°,  it 
becomes  partially  fluid,  and  perfectly  so  at  a  temperature  a  little 
higher  than  this.  Heated  to  700°,  it  sublimes  like  sulphur,  which 
it  closely  resembles  in  many  of  its  properties.  At  a  temperature 
of  212°,  or  a  little  higher,  especially  if  it  has  been  heated  con- 
siderably above  this  and  again  cooled  down,  it  is  viscid,  and  may 
be  worked  like  softened  sealing-wax,  and  drawn  out  into  small 
threads. 

When  heated  in  the  open  air,  it  readily  takes  fire  and  burns, 
exhaling  a  strong  odor  not  unlike  that  of  decaying  horse-radish, — a 
character  by  which  it  may  always  be  distinguished. 


Compounds  of  Selenium  and  Oxygen. 

269.  Selenium  forms  with  oxygen  three  compounds,  SeO,  SeO,,  and 
Se03.  The  latter  two  are  acids,  and  in  many  of  their  properties  quite 
similar  to  sulphurous  and  sulphuric  acids,  to  which  they  correspond  in 
composition. 

QUESTIONS. — 268.  In  what  is  selenium  found?  Describe  its  pro- 
perties. 269.  What  compounds  does  it  form  with  oxygen  ? 


240     COMPOUNDS  OF  SELENIUM  AND  OXYGEN. — TELLURIUM. 

270.  Selenous  Acid— Se02;  eq.,  (39-5  -f-  2  x  8=)  55-5.— To  prepare 

this  acid,  a  retort  contain 
ing  a  mixture  of  chlorate 
of  potash  and  peroxide  of 
manganese  is  connected,  as 
represented  in  the  figure, 
•with  a  tube  bent  downward 
so  as  to  receive  a  quantity 
of  selenium  at  the  lowest 
part.  Heat  is  then  applied 
to  the  chlorate  by  which 
oxygen  gas  is  evolved,  and 
also  to  the  selenium  in  the 
tube.  As  the  selenium 
becomes  heated,  it  burns 
slowly,  with  a  blue  flame, 
and  the  selenous  acid  is  collected  in  the  upper  part  of  the  tube  in 
the  form  of  white  acicular  crystals,  which  are  very  soluble  in  water. 


Preparation  of  SeOa. 


271.  Selenic  Acid-~Se03;  eq.,  (39-5  -f  3  x  8  =)  63-5.— Selenic  acid 
is  prepared  by  burning  selenium  with  nitrate  of  potash,  when  seleniate 
of  potash  is  formed,  from  which  the  acid  may  be  .obtained  in  the  liquid 
form.  Its  chief  interest  is  found  in  its  close  resemblance  to  the  corres- 
ponding sulphur  acid,  S03,  and  in  the  fact  that  it  is  capable  of  dissolving 
gold. 

With  hydrogen  selenium  forms  a  compound,  hydroseleni'c  acid,  HSe, 
which  is  gaseous,  and  irritating  to  the  eyes,  nose  and  Jungs.  It  is  ab- 
sorbed by  water,  like  hydrosulphuric  acid,  and  the  solution,  like  that 
of  hydrosulphuric  acid,  is  decomposed  by  contact  with  the  air. 

The  compounds -of  selenium  with  sulphur,  chlorine  and  bromine  are 
not  of  sufficient  interest  to  require  attention  in  this  work. 


TELLURIUM. 

Symbol,  Te;  Equivalent,  64-5;  Density,  6-2. 

272.  History,  etc. — Tellurium  is  a  rare  substance,  which  has 
sometimes  been  found  native,  but  is  usually  combined  with  the 
metals,  as  gold,  silver,  bismuth  and  lead.  It  is  generally  pre- 
pared from  the  telluride  of  bismuth,  which  is  found  in  Schemintz 
in  Hungary. 


QUESTIONS. — 270.  Describe  the  mode  of  preparing  selenous  acid. 
271.  Describe  selenic  acid.  What  compound  does  selenium  form  with 
hydrogen  ?  272.  Describe  tellurium. 


COMPOUNDS   OP   TELLURIUM  WITH   OXYGEN,  ETC.         241 

Tellurium,  in  some  of  its  physical  properties,  closely  resembles 
the  metals  with  which  it  is  often  associated ;  but  in  its  chemical 
properties  it  is  more  nearly  allied  to  the  non-metallic  elements, 
especially  sulphur  and  selenium. 

When  pure,  it  has  a  clear  white  color,  and  bright  metallic 
lustre  j  and  in  its  general  appearance  is  not  unlike  antimony.  It 
melts  at  a  dull  red  heat,  and,  by  slow  and  careful  cooling,  may 
be  obtained  in  crystals,  the  primary  form  of  which  is  the  rhombo- 
hedron.  At  a  very  high  temperature  it  becomes  gaseous. 


Compounds  of  Tellurium  with  Oxygen,  Efc. 

273.  Tellurium  forms  with  oxygen  two  acid  compounds,  viz.,  tellurous 
acid,  Te02,  and  telluric  acid,  Te03,  which,  as  will  at  once  be  seen,  are 
similar  in  composition  to  the  corresponding  compounds  of  sulphur  and 
selenium. 

With  hydrogen,  also,  like  the  two  elements  just  named,  it  forms  a 
single  gaseous  compound,  hydrotelluric  acid,  HTe,  l;he  smell  of  which  is 
even  more  offensive  than  that  of  hydrosulphuric  acid. 

Tellurium  combines  with  chlorine,  iodine,  bromine,  sulphur,  sele- 
nium, etc. 


GROUP  IV. 

'  ^      Two  elements  which  are  solid  at  ordinary  tempera- 

FHC  PHORUS  [  tureg^  and  similar  ia  many  other  properties.     Many  of 

J  their  compounds  are  isomorphous. 
PHOSPHORUS. 

Symbol,  P;  Equivalent,  32 ;  Density,  1-8  to  2. 

274.  History. — Phosphorus  was  discovered  by  an  alchemist 
of  Hamburg,  in  1669;  and  received  its  present  name  (from 
phns,  light,  and  pherein,  to  carry)  from  the  circumstance  that, 
at  ordinary  temperatures,  it  always  appears  luminous  in  the  dark.r 

QUESTIONS. — 273.  What  is  said  of  the  compounds  of  tellurium  with 
oxygen?     274.  Give  the  history  of  phosphorus. 
21 


242 


PHOSPHORUS. 


It  is  not  found  in  nature  in  a  separate  state  ;  but  in  combination 
with  oxygen  and  lime,  it  is  very  generally  diffused,  being  con- 
tained in  all  fertile  soils,  without  exception,  and  in  many  vegetable 
and  animal  substances. 

275.  Preparation,  —  Phosphorus,  at  the*  present  time,  is  pre- 
pared entirely  from  bones,  which  are  first  heated  in  the  open  air 
until  they  become  white,  so  as  to  destroy  all  the  animal  matter 
they  contain.  More  than  half  their  weight  remains,  which  is 
chiefly  phosphate  of  lime.  This  is  then  ground  to  a  fine  powder, 
and  digested,  for  one  or  two  days.,  with  dilute  sulphuric  acid,  in 
the  ratio  of,  3  parts  of  the  bone  ashes  to  2  parts  of  acid  and  15  or 
20  parts  of  water. 

The  action  of  the  sulphuric  acid  upon  the  phosphate  of  lime,  is 
to  take  away  a  part  of  its  lime,  forming  with  it  sulphate  of  lime; 
and  as  the  whole  of  the  phosphoric  acid  of  the  original  phos- 
phate is  then  in  combination  with  only  a  part  of  its  lime,  it  is 
plain  that  this  must  now  be  a  super-phosphate  of  lime.  This 
latter  is  soluble  in  water,  while  the  sulphate  of  lime  which  has 

been  formed  is  insoluble  ;  more 
water  is  therefore  added,  and  a 
clear  liquid  obtained,  which  is  evi- 
dently solution  of  super-phosphate 
of  lime.  This  liquid  is  now  eva- 
porated until  it  begins  to  be  quite 
thick,  when  it  is  mixed  intimately 
with  charcoal,  in  fine  powder,  and 
thoroughly  dried.  It  is  next  in- 
troduced into  an  earthern  retort, 
a,  which  is  placed  in  a  proper 
furnace,  as  represented  in  the 
figure;  and  to  the  neck  of  the 

Preparation  of  Phosphorus. 


attached,  which  connects  with  a  vessel  of  water.  The  heat  is 
then  gradually  raised,  when  the  phosphorus  distils  over,  and  is 
condensed  in  the  water.  Much  combustible  gaseous  matter,  also, 


QUESTION. — 275.  Describe  the  mode  of  preparing  phosphorus. 


PHOSPHORUS.  248 

comes  over  and  escapes  by  the  second  tube,  inserted  in  the 
water- vessel. 

The  affinity  of  charcoal  for  oxygen  at  low  temperatures  is 
not  very  considerable,  but  when  highly  heated  it  is  intense,  and 
sufficient  to  abstract  the  oxygen  from  the  phosphoric  acid  of  the 
acid  phosphate  of  lime,  causing  the  liberation  of  the  phosphorus. 
This,  taking  the  gaseous  state,  distils  over  and  is  condensed  to 
the  liquid  form,  and  finally  solidified. 

The  phosphorus  thus  procured  is  still  impure,  and  is  to  be 
melted  in  hot  water,  and  pressed  through  porous  leather. 

276,  Properties, — Pure  phosphorus  is  of  a  light  flesh-color, 
and  nearly  transparent.  At  common  temperatures,  ifc  is  a  soft 
solid,  of  specific  gravity  about  2,  and  may  easily  be  cut  with  la 
tnife.  At  108°  it  fuses,  and  at  554°  is  converted  into  vapor, 
which  has  a  density  of  4-326.  It  is  soluble,  by  the  aid  of  heat, 
in  naphtha,  in  fixed  and  volatile  oils,  and  in  some  other  liquids. 
By  the  fusion  and  slow  cooling  of  a  considerable  quantity,  it  may 
be  crystalized,  and  also  from  its  solution  in  bisulphide  of  carbon. 
The  crystals  belong  to  the  monometric  system. 

It  is  usually  seen  in  long,  slender  sticks,  of  a  waxy  lustre, 
which  are  made  by  melting  the  phosphorus  under  water  and 
pouring  it  into  glass  tubes. 

Phosphorus  may  be  distilled  without  difficulty.  For  a  small 
operation,  fit  a  green  glass  retort  to  a  tube  bent,  as  represented 
in  the  figure,  and  having  its- 
extremity  drawn  out  to  a  fine 
point,  but  not  closed.  Sepa- 
rate the  retort  and  tube,  and 
put  in  the  first  a  small  quantity 
of  phosphorus,  and  in  the  latter 
a  little  water ;  and  again  con- 
.nect  them  firmly  together.  If 
now  the  retort  is  carefully 

heated,  the  phosphorus  will  gradually  distil  over  and  collect  in 
the  water  in  the  lowest  part  of  the  tube. 

QUESTIONS. — What  is  the  effect  produced  by  the  charcoal  ?  276.  De- 
scribe phosphorus.  In  what  is  it  soluble  ?  In  what  form  is  it  usually 
••ml 


244 


PHOSPHORUS. 


Combustion  of  Phos- 


Phosphorus  is  exceedingly  inflammable.  Exposed  to  the  air, 
at  common  temperatures,  it  undergoes  slow  combustion,  emits 
a  white  vapor  of  a  peculiar  alliaceous  odor,  appears  distinctly 
luminous  in  the  dark,  and  is  gradually  consumed.  On  this 
account,  phosphorus  should  always  be  kept  under  water.  In 
the  open  air,  even  the  heat  of  the  hand,  aided  by  the  slightest 
friction,  is  sufficient  to  inflame  it ;  and  it  should  therefore  always 
be  handled  with  the  greatest  caution.  It  burns  in  the  air  with  a 
brilliant,  yellowish-white  light  and  intense 
heat;  but  in  oxygen  gas,  its  combustion  is 
particularly  splendid.  A  good  method  for 
performing  the  experiment  is  to  place  a 
piece  of  phosphorus  in  a  small  cup  on  a 
stand,  a  few  inches  high,  in  a  basin  of- 
water,  and,  having  ignited  the  phosphorus 
by  touching  it  with  a  piece  of  heated  wire, 
dexterously  to  place  over  it  a  large  bell-glass, 
previously  filled  with  oxygen.  By  careful 
Oxygen'  management,  but  little  of  the  oxygen  will 
be  lost.  It  may  also  be  made  to  burn  under  warm  water,  by 
forcing  a  current  of  oxygen  upon  it  by 
means  of  a  gas-bottle,  or  a  flexible  tube, 
leading  from  a  gasometer.  A  red  suboxide 
is  formed  which  readily  takes  fire  in  the 
open  air. 

The  red  crust  which  forms  upon  the  surface 
of  pieces  of  phosphorus  exposed   to  the  action 
of  light,  is  believed  to  be  a  peculiar  isomeric,  or 
Combustion  of  Phos-     allotpopic  (173)  condition  of  this  substance.      It 
Wa°teUr8  *  ma?  be  obtained,  by  keeping  a  quantity  of  phos, 

phorus  for  several  hours,  at  a  temperature  of 

460°  to   480°,  in   a  gas   which  does  not  act  upon  it,  as  nitrogen  or 
hydrogen. 

This  red  or  amorphous  phosphorus  differs  essentially  from  ordinary 
phosphorus.  Its  melting  point  is  about  482°,  and  it  is  non-luminous  in  the 
air  at  ordinary  temperatures.  Heated  to  500°,  it  changes  to  ordinary 
phosphorus. 

QUESTIONS. — How  is  phosphorus  affected  in  the  open  air  ?  How  is  it 
usually  preserved  ?  May  it  be  distilled  ?  What  is  said  of  its.  com- 
buation  in  oxygen  gas  ?  How  may  it  be  made  to  burn  under  water  ? 


COMPOUNDS   OF   PHOSPHORUS   AND   OXYGEN.  245 

277.  Uses. — Phosphorus  is  now  used  in  large  quantities  in  the 
manufacture  of  friction-matches,  which  ignite  by  slight  friction. 
For  this  purpose  it  is  made  into  a  paste,  with  gum  or  glue,  by 
which  it  is  made  to  adhere  to  small  pieces. of  wood  or  paper  pre- 
viously dipped  in  melted  sulphur,  and  is  also  protected  from  the 
action  of  the  air. 

The  paste  is  sometimes  mixed  with  nitrate  or  chlorate  of  potash, 
or  oxide  or  nitrate  of  lead,  but  this  is  not  necessary.  Occasionally, 
fine  emory  or  powdered  glass  is  mixed  in  the  paste,  to  increase  the 
friction. 

Phosphorus  is  of  great  service  in  the  laboratory,  and  has  been 
sometimes  used  in  medicine. 


Compounds  of  Phosphorus  and  Oxygen. 

278.  There  are  four  compounds  of  phosphorus  and  oxygen,  the 
atomic  constitution  of  which  appears  to  Be  P20,PO,P03  and  P05. 
The  last  three  are  acids ;  but  only  one  of  these,  the  last,  will  be 
specially  described. 

279.  Dinoxide  of  Phosphorus — P20. — This  compound  is  prepared  by  the 
combustion  of  phosphorus  under  hot  water,  as  in  paragraph  276.     Atmo- 
spheric air  may  be  substituted  for  the  oxygen.     The  oxide  appears  as 
flocculi  of  a  brick-red  color.     It  absorbs  oxygen  from  the  air,  and  mixed 
with  phosphorus  it  renders  it  more  combustible. 

280.  Hypophosphorous  Acid  —  PO. —  May  be   obtained   as  a  syrupy 
liquid,  but  cannot  be  crystalized.     It  cannot  be  obtained  separate  from 
•water. 

281.  Phosphorous  Acid— P03.  —  Phospho- 
rous acid   may  be  prepared  by  the   action 
of  the    air   upon  sticks   of  phosphorus,  at 
ordinary  temperatures.      For  this  purpose, 
place  a  few  sticks  of  phosphorus  in  a  funnel 
under  a   bell-glass,  as   represented    in  the 
figure.     The  glass  is  supported  a  little  above 
the  table,  to  allow  the  air  to  enter.     Reg- 
nault  advises  to  put  the  sticks  of  phosphorus 

in  small  glass  tubes,  having  capillary  aper-        "^- :_=^ 

tures  for  the  acid  to  pass  through  a~s  it  is  Preparation  of  POs. 

QUESTIONS. — 277.  What  use  is  made  of  phosphorus  ?  How  are  friction- 
matches  made  ?  278.  What  compounds  of  phosphorus  and  oxygen  are 
there  ?  279.  How  may  dinoxide  of  phosphorus  be  prepared  ?  281.  How 
may  phosphorous  acid  be  prepared  f 


246 


COMPOUNDS   OF   PHOSPHORUS  AND  OXYGEN. 


formed,  but  they  are  not  essential.  Too  large  quantities  of  phosphorus 
should  not  be  used  at  once. 

282.  Phosphoric  Acid— P05;  eq.,  (32 -f  40=)  72.  — This 
acid  is  formed  by  burning  phosphorus  in  air  or  in  oxygen  gas,  as 
in  the  experiment  given  above  (27,6).  To  prepare  it  perfectly 
anhydrous,  the  receiver  should  be  placed  over  mercury,  and  the 
oxygen  or  air  supplied  should  be  perfectly  dry.  The  acid  appears 
as  a  dense  white  vapor,  which  is  gradually  precipitated,  and  may 
be  collected.  In  the  open  air  it  at  once  absorbs  moisture.  If  the 
white  flakes  are  collected  and  ignited,  the  mass,  after  cooling,  is 
semi-transparent,  and  is  called  glacial  phosphoric  acid.  This 
acid  may  also  be  formed  from  calcined  bones. 

To  prepare  the  common  acid,  a  very  good  mode  is  to  digest 
phosphorus  in  nitric  acid,  with  the  aid  of  heat.  One  part  of 

phosphorus,  with  13 
parts  of  the  acid,  of 
specific  gravity  1-20,  is 
placed  in  a  glass  retort 
which  connects  with  a 
receiver  that  is  kept 
cold  by  a  stream  of  cold 
water,  as  shown  in  the 
figure,  and  heat  applied. 
Red  fumes  of  nitrous 

Preparation  of  POs. 

acid  are  given  off,  and 

the  phosphorus  rapidly  consumed.  The  liquid  collected  in  the 
receiver  is  now  to  be  poured  back  into  the  retort,  and  heated 
until  the  water  and  any  remaining  nitric  acid  are  expelled.  On 
cooling  it  will  become  solid,  and  present  the  same  appearance  as 
glacial  phosphoric  acid  just  described.  The  acid  thus  obtained 
contains  1  eq.  of  water  for  each  eq.  of  the  acid,  and  is  called  mono- 
hydrated  acid. 

The  anhydrcfus  phosphoric  acid  has  a  very  strong  affinity  for 
water,  and  when  thrown  into  it,  unites  with  it  with  great  energy, 
often  producing  slight  explosions,  in  consequence  of  the  heat  pro- 

QUESTIONS. — i82.  What  is  the  composition  of  phosphoric  acid  ?  How 
is  it  prepared  ?  How  by  the  use  of  nitric  acid  ?  What  is  said  of  its 
compounds  with  water  ? 


COMPOUNDS  OP  PHOSPHORUS  AND  HYDROGEN. 


247 


duced.  With  water  it  forms  three  different  compounds,  as  fol- 
lows, the  first  two  of  which  have  been  called,  respectively,  meta- 
phosphoric,  and  pyrophosphoric  acids. 

Monohydrated,  or  metaphosphoric  acid,    P05,HO. 
Bihydrated,  or  pyrophosphoric  acid,          P05,2HO, 
Trihydrated,  or  common  phosphoric  acid,  P05,3HO. 

These  three  acids,  or  rather  compounds  of  acid  and  water,  can- 
not be  distinguished  from  each  other  by  external  appearance,  but 
dissolved  in  water  they  manifest  chemical  characteristics  which 
render  them  quite  distinct;  they  also  form  salts,  which,  though 
much  alike  in  their  general  properties,  are  nevertheless  easily  dis- 
tinguished from  each  other  by  the  proper  tests. 


Compounds  of  Phosphorus  and  Hydrogen. 

There  are  several  compounds  of  phosphorus  and  hydrogen,  but 
one  only  will  claim  attention  from  us,  the  common  phosphuretted 
hydrogen,  PH3.  The  o'thers  are  P2H,  and  PH2. 

283.  Phosphide  of  Hydrogen— PH3 ;  eq.,  (32  +  3  =)  35.— 

This  gaseous  substance,  called  also  phosphuretted  hydrogen,  13 
best  prepared  by  heating  some  sticks  of  phosphorus  in  a  strong 
solution  of  caustic  pot- 
ash, in  a  small  glass 
retort,  which,  at  the 
beginning  of  the  opera- 
tion, should  be  quite 
filled  with  the  mate- 
rials. If,  then,  the 
mouth  of  the  retort  is 
made  to  dip  slightly  in 

i       .          /.  ,  PIIs  spontaneously  combustible. 

a  basin  of  water,  each 

bubble  of  the  gas,  as  it  breaks  into  the  air,  will  burst  into  a  flame, 


QUESTIONS. — 283.  What  phosphide  of  hydrogen  is  mentioned 
is  it  prepared  ? 


How 


248  COMPOUNDS   OF   PHOSPHORUS   AND    HYDROGEN. 

with  the  formation  of  beautiful  wreaths  of  smoke  of  phosphoric 
acid,  as  shown  in  the  figure. 

In  the  presence  of  potash  phosphorus  has  the  property  of 
decomposing  water,  especially  if  the  temperature  be  raised  ;  the 
oxygen  and  the  hydrogen  both  combining  with  separate  portions 
of  the  phosphorus,  producing  the  teroxide  of  phosphorus  (phos- 
phorous acid)  and  the  terphosphide  of  hydrogen.  Thus, 

2P  +  3EO  +  KO  =  KO,P03  +  PH3. 

Instead  of  potash,  milk  of  lime  may  be  used  with  the  same 
result. 

Still  another  method  of  procuring  it  is  to  decompose  phosphide 
of  calcium  by  water,  or  dilute  hydrochloric  acid  ;  but  when  this 
acid  is  used,  the  gas  which  is  given  off  is  not  spon- 
taneously inflammable.     It  seemsi  to  be  very  well 
determined   that  the  spontaneous  combustion  of 
this  gas,  in  certain  cases,  is  owing  to  the  presence 
of  the  vapor  of  another  phosphide  of  hydrogen  con- 
taining  proportionally    more   phosphorus,   which 
may  be  separated  by  passing  the  gas  through  a 
PH3  gpontane-    tube  surrounded  by  a  freezing  mixture. 

Qther  combustible  gases,  as  hydrogen,  are  made 
to  inflame  spontaneously  by  receiving  a  portion  of 
the  vapor  of  this  inflammable  phosphide. 

To  prepare  phosphide  of  calcium,  select  a  tube  of  green  glass,  half  an 
inch  in  diameter  and  a  foot  long  ;  seal  one  end  hermetically,  and  bend 

it  a  little,  as  represented  in  the  figure. 

In   the   sealed   end    put    some     pieces 

"lam       of  phosphorus,    and^  then,   holding  the 

T%&      straight  part  in   a  horizontal   position, 

...     ,n  ,  .          introduce  some  lumps  of  well   burned 
Preparation  of  Phosplnde  of  Calcmm.  Ume  .g 


combusti- 


next  to  be  heated  to  redness  by  means  of  burning  charcoal,  when  heat  is 
also  to  be  applied  to  the  phosphorus  sufficient  to  volatilize  it;  and  the 
Vapor  coming  in  contact  with  the  heated  lime,  at  once  unites  with  it  to 
form  the  phosphide  of  calcium.  This  should  be  preserved  in  bottles 
•with  close  stoppers  ;  but  even  then  it  gradually  undergoes  decomposition. 

Terphosphide  of  hydrogen  is  a  colorless  gas,  with  a  very  disagreeable 

QUESTIONS.  —  Describe  some  of  the  properties  of  phosphide  of  hydrogen, 
To  what  is  its  spontaneous  combustion  owing  ? 


OTHER   COMPOUNDS   OP   PHOSPHORUS. 


249 


odor,*  and  is  irrespirable ;  100  cubic  inches  of  it  weigh  36-75  grains, 
giving  it  a  specific  gravity  of  1-18. 

1  vol.  of  phosphorus  vapor  weighs    4-326 
6  vols.  of  hydrogen  weigh  (-069  X  6)     -414 

Forming  4  vols.  of  the  terphosphide,  4-740 
One  volume  therefore  weighs,  or  the  density  of  the  gas  is,  1-186 


Other  Compounds  of  Phosphorus. 

Phosphide  of  Nitrogen,  N2P,  is  a  white  solid,  which  is  infusible  even 
at  a  red  heat. 

284.  Chlorides  of  Phosphorus. — There  are  two  chlorides  of  phosphorus, 
PC13,  and  PC16,  corresponding  in  composition  to  phosphorous  and  phos- 
phoric acids. 

The  Terchloride  of  Phosphorus  is  formed  in  the  same  manner,  and  by 
using  the  same  apparatus,  as  chloride  of  sulphur  (266).  The  chlorine 


Preparation  of  PCR 


is  formed  in  the  flask  A,  and  after  being  washed  in  water  and  dried  in 
the  chlorine  of  calcium  tube,  is  brought  in  contact  with  the  vapor  of  phos- 

*  Those  who  have  observed  the  odor  of  this  gas,  and  that  of  the  liquid  emitted  by  the 
American  skunk  (Mephitis  Americana)  when  disturbed,  cannot  but  have  noticed  the 
resemblance  between  them;  which  seems  to  render  it  probable  that  the  fluid  emitted  by 
the  skunk  contains,  in  solution,  a  portion  of  the  gas,  or  some  other  nearly-related  com- 
pounds of  the  same  substances.  This  is  rendered  still  more  probable  from  the  fact,  that 
the  fluid,  when  emitted  by  the  animal  in  the  dark,  is  distinctly  phosphorescent. — Set 
Godman's  Natural  History,  vol.  1.  289 :  Philadelphia  Edition,  1829. 

QUESTION. — 284.  What  chlorides  of  phosphorus  are  mentioned? 


250 


ARSE  NIC. 


phorus  in  the  retort,  D,  where  the  chloride  is  formed,  and  afterwards  con« 
densed  in  the  receiver  E,  which  is  kept  cool  by  a  stream  of  cold  water 
It  is  a  colorless  liquid,  of  a  density  of  l-45j  which  boils  at  about  172°. 

285.  Percbloride  of  Phosphorus  is  formed  by  saturating  the  preceding 
with  chlorine.  It  is  a  solid,  having  its  point  of  fusion,  and  also  its  boil- 
ing point,  at  about  298°. 

Bromine  and  sulphur  combine  readily  with  phosphorus, 
but  the  compounds  are  not  important. 

Iodide  of  Phosphorus  is  formed  by  bringing  the  two  sub- 
stances  together  in  a  vessel  where  as  little  air  may  have 
admission  as  possible.  It  forms  a  dark-colored  mass. 
These  two  substances  afford  one  of  the  few  instances  in 
which  reaction  takes  place  between  two  solids.  Let  a 
few  crystals  of  iodine  be  dropped  into  a  wine-glass,  upon 
a  small  piece  of  phosphorus,  and  immediately  place  over 
it  a  bell-glass.  By  the  heat  produced,  the  phosphorus 
will  be  inflamed  and  a  portion  of  the  iodine  sublimed ; 
and  the  white  cloud  of  phosphoric  acid  (152),  mingling 
with  the  dense  iodine  vapor,  presents  to  the  eye  a  very 
pleasing  appearance. 


Prep,  of  Iodide 
of  Phosphorus. 


ARSENIC. 
Symbol,  As;  Equivalent,  75;  Density,  5-88. 

*  286.  History  and  Preparation. — Arsenic  has  very  generally 
been  Classed  with  the  metals,  chiefly  on  account  of  its  metallic 
lustre,  and  comparatively  high  specific  gravity;  but,  in  its 
chemical  properties,  it  is  much  more  closely  allied  to  the  metal- 
loids, with  which  it  is  here  classed. 

Arsenic  sometimes  occurs  native,  but  usually  it  is  found  in  com- 
bination with  the  metals,  and  especially  with  iron  and  cobalt. 
The  substance  itself,  or  some  of  its  compounds,  seems  to  have 
been  known  from  the  earliest  times. 

It  may  readily  be  prepared  by  "heating  the  mineral  called  mis- 
pickel,  which  is  a  natural  compound  of  arsenic,  sulphur  and  iron, 
in  close  vessels,  by  which  the  arsenic  is  expelled  and  the  sulphide 

QUESTIONS. — 285.  How  is  iodide  of  phosphorus  prepared  ?  What  is 
said  of  the  action  of  iodine  and  phosphorus  upon  each  other  ?  286.  Why 
has  arsenft  often  been  classed  with  the  metals  ?  Why  is  it  here  classed 
with  the  metalloids  ?  With  what  is  it  usually  found  combined  ? 


COMPOUNDS   OP   ARSENIC    AND   OXYGEN.  251 

of  iron  remains.  By  again  heating  it  with  black-flux,  the  arsenic 
is  obtained  nearly  pure.  If  the  pulverized  mineral  is  well  mixed 
with  black-flux  at  the  beginning,  and  no  air  admitted  into  the 
apparatus,  a  single  operation  will  afford  it  in  great  purity. 

Let  a  common  Hessian  crucible  be  half  filled  with 
the  mixture,  and  then  place  ano.ther  crucible,  a  size 
smaller,  in  an  inverted  position  above  it,  as  shown  in 
the  figure,  carefully  luting  them  at  their  junction.  A 
moderate  heat  should  then  be  applied  to  the  lower 
crucible  and  very  gradually  raised.  The  arsenic  will 
be  sublimed  from  the  mixture  and  condensed  in  small 
crystals  in  the  inverted  crucible,  which  should  have  a 
very  small  aperture  in  the  bottom,  to  allow  the  air  to 
escape  as  the  heat  is  raised. 

287.  Properties. — Arsenic  is  a  brittle  substance,  of  a  dark 
color,  and  feeble  metallic  lustre.  Heated  to  about  356°,  it  is 
sublimed,  without  first  melting,  as  is  the  case  with  most  solids. 
Its  vapor  has  a  strong  garlic  odor,  by  which  its  presence  may  be 
recognised,  and  a  density  of  10-37.  Heated  in  the  open  air,  it 
readily  takes  fire  and  burns  with  a  livid  flame. 

Arsenic  is  often  sold  under  the  very  improper  names  of  cobalt 
and  fly -powder. 


Compounds  of  Arsenic  and  Oxygen. 

288.  Two  compounds  only  of  arsenic  and  oxygen  are  known, 
both  of  which  are  acids,  and  in  composition  correspond  to  phos- 
phorous and  phosphoric  acids. 

289.  Arsenious  Acid— As03;  eq.,  (75  +  3  x  8  =)  99.— This 
compound  is  the  arsenic,  or  rats'  bane,  of  commerce,  well  known 
as  a  destructive  poison.     It  is  always  produced  when  arsenic  or 
its  ores  are  heated  in  the  open  air.     It  is  usually  sold  in  a  state 

QUESTIONS. — How  may  arsenic  be  separated  from  its  compounds? 
287.  Describe  arsenic.  What  is  said  of  its  odor?  288.  What  com- 
pounds  of  arsenic  and  oxygen  are  known  ?  289.  By  what  names  is 
arsenious  acid  often  known. 


252  COMPOUNDS   OF   ARSENIC   AND   HYDROGEN. 

of  fine  white  powder ;  but  when  first  sublimed,  it  is  in  the  form 
of  brittle  masses,  more  or  less  transparent,  colorless,  of  a  vitreous 
lustre,  and  conchoidal  fracture.  This  glass,  which  may  also  be 
obtained  by  fusion,  gradually  becomes  opaque  without  undergoing 
any  apparent  change  of  constitution,  but  becomes  more  soluble  in 
water  than  before.  Its  specific  gravity  is  3-7.  At  880°  it  is 
volatilized,  yielding  vapors  which  do  not  possess  the  odor  of 
garlic,  and  which  condense  unchanged  on  cold  surfaces.  If  thrown 
on  burning  charcoal,  the  garlic  odor  is  perceived,  because  of 
the  reduction  of  the  oxide  by  the  carbon. 

Destructive  as  this  substance  is  to  the  animal  system,  in  minute  doses 
it  is  sometimes  used  in  medical  practice;  and  in  some  countries,  as  in 
parts  of  Austria  and  Hungary,  it  is  habitually  used  much  in  the  same 
manner  as  narcotics,  and  even  administered  to  horses.  The  effect  is 
said  to  be  to  give  a  roundness  and  fulness  of  form,  and  clearness  and 
freshness  to  the  complexion.  Horses  accustomed  to  receive  it  in  their 
food,  have  a  fat  and  plump  appearance,  and  bright  and  glossy  skins.  It 
also  improves  their  breathing. 

This  substance  is  so  frequently  used  to  destroy  life,  that  its  detection 
Ji  suspicious  cases  becomes  an  important  object;  but  we  reserve  our 
remarks  on  this  point  until  some  others  of  the  many  compounds  of  arsenic 
have  been  described 

290.  Arsenic  Acid— As06;  eq.,  (75  -f  8  x  5  =)  115.— This  acid  may 
be  formed  by  dissolving  arsenious  acid,  just  described,  in  nitric  acid 
mixed  with  a  little  of  the  hydrochloric,  and  evaporating  to  dryness.  It 
is  a  powerful  acid,  much  resembling  phosphoric  acid  (247) ;  with 
•which  it  is  isomorphous.  Its  salts  are  also  isomorphous  with  the  salts 
of  phosphoric  acid. 


Compounds  of  Arsenic  and  Hydrogen. 

291.  Two  compounds  of  these  elements  are  known,  one  of  which  is 
solid,  and  the  other  gaseous.     Of  the  former,  little  is  known,  with  cer- 
tainty, and  we  therefore  do  not  further  allude  to  it. 

292.  Arsenido  of  Hydrogen,  Arseniuretted  Hydrogen  —  AsH3;    eq., 
(75  _j_  3  —)  78. — This  gas  is  evolved  when  arsenide  of  tin  or  zinc  is 
treated  with  strong  hydrochloric  acid,  or  when  sulphuric  or  hydrochloric 
acid  is  made  to  act  upon  zinc  or  iron  in  the  presence  of  any  soluble  com- 
pound of  arsenic. 

To  prepare  it,  pour  upon  some  pieces  of  zinc  diluted  sulphuric  acid 
•with  a  few  drops  of  solution  of  arsenious  acid  ;  the  gas,  which  burns  with. 
a  feeble  blue  flame,,will  be  at  once  rapidly  evolved. 

QUESTIONS. — Describe  arsenious  acid.  For  what  purpose  is  it  often 
used  ?  290.  To  what  other  acid  is  arsenic  acid  analogous  ?  292.  How 
is  arsenide  of  hydrogen  prepared  ? 


COMPOUNDS   OP  ARSENIC   WITH   SULPHUR,  *ETC.  253 

When  thus  prepared,  the  reactions  are  as  indicated  in  the  following 
formula,  the  zinc  being  oxydized  at  the  expense  of  the  oxygen  both  of  the 
water  and  the  arsenious  acid.  Thus, 

'   6Zn  -f  3 HO  -f  As03  -f  6S03  =  6  (ZnO,S03)  -f  AsH3. 

The  gns  has  a  peculiar  nauseating  odor,  and  is  exceedingly  poisonous- 
Its  density  is  2-69,  and  by  a  cold  of  — 22°  it  is  converted  into  a  liquid 
under  the  ordinary  atmospheric  pressure.  By  chlorine  it  is  instantly 
decomposed,  chloride  of  arsenic  and  hydrochloric  acid  being  formed. 
By  solution  of  blue  vitriol  it  is  rapidly  absorbed,  and  arsenide  of  copper 
precipitated. 

The  equivalent  "of  this  gas,  AsH3,  answers  to  4  vols.,  which  is  thus 
constituted: 

1  vol.  of  arsenic  vapor  weighs  10-370 
6      "       hydrogen  "          -414 

4  vols.  arsenide  of  hydrogen,  10-784 

Weight  of  one  vol.,  or  the  calculated  density  of  the  gas,  2-696. 
We  shall  have  occasion  to  speak  of  this  compound  again  in  connection 
with  the  detection  of  arsenic. 


Compounds  of  Arsenic  with  Sulphur  and  Other  Elements. 

293.  Sulphides  of  Arsenic. — The  bisulphide  of  arsenic,  AS2,  is  found 
native,  and  called  realgar  by  mineralogists.  It  may  also  be  fonned  by 
art.  It  is  of  a  dull  red  color.  The  tersulphide,  AsS3,  is  the  orpiment, 
or  king's  yellow  of  commerce.  It  is  formed  artificially  by  passing  a  cur- 
rent of  hydrosulphurio  acid  through  an  arsenic  solution  containing  a 
little  free  acid.  It  is  also  found  as  a  natural  production,  and  is  of  a 
bright  yellow  color,  and  is  sometimes  called  sulpharsenious  add.  A  third 
compound  of  these  elements,  the  pentasulphide  of  arsenic,  AsS5,  called 
also  sulpharsenic  acid,  is  formed  by  mixing  solutions  of  hydrosulphuric 
and  arsenic  acids.  It  forms  slowly,  and  some  days  are  often  required 
before  the  whole  is  precipitated. 

The  compounds  of  arsenic  with  chlorine,  iodine,  phosphorus,  &c.,  will 
be  found  described  in  larger  works. 

QUESTIONS. — Describe  the  reactions  which  take  place  in  the  prepara- 
tion of  arsenide  of  hydrogen.  What  are  some  of  the  properties  of  this 
'  gas  ?  293.  What  is  realgar  f  What  is  orpimenl? 

22 


254  »     DETECTION    OP    ARSENIC. 


Detection  of  Arsenic. 

294.  Poisoning  by  arsenious  acid  is  at  the  present  day, .unfor- 
tunately, very  common;  and  it  therefore  becomes  a  matter  of 
special  importance  to  be  able  with  certainty  to  detect  the  instru- 
ment of  death. 

295.  There  are  as  many  as  ten  or  twelve  different  tests  for 
arsenic,    but   we   shall    confine    our   remarks    to    some   of   the 
most  important.     A  single  test  should  never  be  relied  on,  but 
several  different  ones  should  always  be  applied  to  separate  por- 
tions of  the  suspected  substance. 

I.  Marsh's  Test. — Put  into  a  two  or  four  ounce  vial  some  pieces  of 
clean  zinc,  and  pour  on  them  a  small  quantity  of  dilute  oil  of  vitriol 
(oil  of  vitriol  1  part,  and  water  8  parts),  and  insert  a  cork 
with  a  small  tube,  as  shown  in  the  figur*e.  Very  soon 
hydrogen  gas  will  begin  to  be  evolved,  as  in  the  prepara- 
tion of  hydrogen.  After  a  little  time  the  jet  of  hydrogen 
may  be  inflamed ;  and  if  all  the  materials  used  were  pure, 
a  piece  of  glass  or  porcelain  held  in  the  flame  will  receive 
no  stain,  but  only  a  deposition  of  moisture  from  the  com- 
bustion of  the  hydrogen. 

The  cork  and  tube  being  now  removed,  introduce  some 
of  the  suspected  substance,  or  water  in  which  the  suspected 
substance  has  been  digested,  with  the  aid  of  heat  if  ueces- 
Marsh's  Test,  sary,  and  immediately  replace  the  cork  and  tube.  In  a 
little  time  the  jet  of  gas  may  be  relighted  ;  and  if  any  appre- 
ciable quantity  of  arsenious  acid  is  present,  a  piece  of  clean  glass  or 
porcelain  held  in  the  flame  will  at  once  receive  a  black  stain  upon  its 
surface,  caused  by  a  deposition  of  arsenic. 

If  the  quantity  of  arsenious  acid  present  is  large,  the  flame  will  be 
of  a  pale  color,  and  the  blackening  of  the  glass  held  in  the  flame  will  be 
instantaneous  ;  but  if  the  quantity  be  small,  the  blackening  effect  will  be 
produced  only  after  a  little  time. 

The  deposition  of  arsenic  here  is  from  the  arsenide  of  hydrogen, 
•which  is  formed  in  the  manner  heretofore  (292)  explained.  The  cold 
substance  held  in  the  flame  causes  the  deposition  of  the  arsenic  while 
the  hydrogen  is  consumed. 

This  is  perhaps  the  most  delicate  test  of  arsenic  known,  but  in  using  it 
some  precautions  must  always  be  observed  to  avoid  mistake.  In  some 
cases,  where  organic  substances  are  present,  spots  similar  to  those  pro- 
duced by  arsenic  may  be  formed,  that  may  be  mistaken  for  arsenic  by 

QUESTIONS. — 295.  What  is  said  of  the  number  of  tests  for  arsenic? 
Describe  Marsh's  test.  From  what  is  the  arsenic  deposited?  What  is 
Baid  of  the  delicacy  of  this  test  ? 


DETECTION  OF  ARSENIC.  255 

the  inexperienced  ;  and  antimony  will  form  spots  very  much  lite  those 
of  arsenic.  Means  must  therefore  be  adopted  to  test  the  material  form- 
ing the  dark  spot  upon  the  porcelain.  For  this  purpose,  it  will  generally 
be  sufficient  to  hold  the  spot  a  few  minutes  in  the  flame  of  a  spirit-lamp  ; 
if  the  deposite  be  arsenic  it  will  be  volatilized,  and  disappear,  but  if  pro- 
duced by  antimony  or  other  substances,  it  will  remain.  So  also  arsenic 
spots,  exposed  a  few  minutes,  at  a  moderately  elevated  temperature,  to 
vapor  of  iodine,  become  yellow,  and  then  subsequently  disappear  by 
exposure  to  the  air. 

II.  Reinch's  Test. — In  a  portion  of  the  suspected  liquid,  made  acid  by 
hydrochloric  acid,  place  a  piece  of  metallic  copper,  previously  filed  per- 
fectly bright,  and  heat  the  whole  nearly  to  the  boiling  point.     If  any 
appreciable  quantity  of  arsenious  «acid  be  present,  the  arsenic  will  be 
deposited  upon  it  as  a  gray  crust  of  a  metallic  lustre. 

III.  Test  by  Hydrosulphuric  Acid. — Through  a  portion  of  the  sus- 
pected substance,  supposed  to  be  in  the  liquid  form,  acidulated  with 
muriatic  acid,  pass  a  current  of  hydrosul- 

phuric  acid  gas  for  half  an  hour,  and  then 
boil  it  a  few  moments ;  if  arsenic  be  pre- 
sent, a  yellow  precipitate — orpiment  (293) 
— will  be  formed.  The  mode  of  passing  the 
current  of  gas  through  the  liquid  will  be 
seen  by  the  accompanying  figure.  The 
materials  for  producing  the  gas  are  put  into 
a  flask,  and  a  tube,  bent  twice  at  right 
angles,  is  inserted  through  a  cork,  so  as  to 

be  air-tight ;  the  other  end  is  then  immersed  

in  the  liquid,  contained  in  a  glass  vessel,  so  Test  by  Hydrosulphuric  Acid, 
as  to  reach  near  the  bottom,  and  the  gas,  as 

it  escapes,  bubbles  through  the  liquid.  The  mode  is  the  same  as  before 
described  (263).  The  precipitate  (orpiment)  thus  formed,  is  entirely 
soluble  in  aqua  ammoniae,  and  in  solutions  of  the  alkalies. 

IV.  Test  by  Ammonia-Nitrate  of  Silver. — Nitrate  of  silver  forms  with 
arsenious    acid  solutions  a  precipitate  of  arsenide  of  silver,  which  is 
of  a  peculiar  canary  yellow  color,  and  is  soluble  in  nitric  acid.     To 
ensure  the  formation  of  this  precipitate,  the  arsenious  solution  should 
be  Ilightly  alkaline,  and  therefore  the  ammonia-nitrate  of  silver  is  used 
in  preference  to  the  simple  nitrate.     This  is  prepared  'by  pouring  into 
the  nitrate  of  silver  solution  aqua  ammonia,  until  the  precipitate  at  first 
thrown  down  is  nearly  all  dissolved. 

A  precipitate  very  similar  in  its  appearance  to  the  above  would  be 
produced  'by  phosphoric  acid  in  the  suspected  liquid  ;  so  that  the  pre- 
cipitate formed  by  use  of  this  test  should  always  be  further  examined, 
before  any  reliance  is  placed  upon  it. 

V.  Test  by  Ammonia-Sulphate  of  Copper. — Solution  of  sulphate  of  cop- 
per produces  in  neutral  or  alkaline  solutions  of  arsenious  compounds  a 
beautiful  green  precipitate,  sometimes  called  Scheele's  green.     In  making 

QUESTIONS.—  Describe  Reinch's  test.  Describe  the  test  with  hydro- 
sulphuric  acid.  Describe  the  test  with  ammonia-nitrate  of  silver.  Describe 
the  mode  of  Jesting  with  ammonia-sulphate  of  copper.  What  will  be  the 
color  of  the  precipitate  ?  • 


256          DETECTION  OP  ARSENIC. 

the  experiment,  it  is  best  to  use  the  ammonia-sulphate  of  copper,  which 
is  prepared  by  pouring  into  a  solution  of  blue  vitriol,  aqua  ammonise, 
until  the  precipitate  at  first  formed  is  nearly  all  redissolved,  as  in  the 
corresponding  preparation  of  ammonia-nitrate  of  silver. 

But  this  test  also  may  form  with  other  substances  a  precipitate  similar 
in  appearance  to  the  above,  so  that  further  examination  should  always 
be  made. 

VI.  Flandin  and  Danger's  Test. — Dry  the  suspected  substance  (sup- 
posed to  be  organic,  as  sugar  or  starch,)  and  treat  it  with  one-fourth  of 
its  weight  of  the  strongest  oil  of  vitriol,  and  apply  heat  until  it  is  quite 
dry ; — the  whole  will  now  be  reduced  to  a  black,  friable  mass,  which  can 
easily  be  pulverized,  and  is  then  to  be  boiled  with  strong  nitric  mixed 
with  a  little  hydrochloric  acid.     By  1&is  process  the  arsenic,  in  whatever 
form  it  may  be,,  is  converted  into  arsenic  acid,  which  after  the  whole  has 
been  again  evaporated  to  dryness,  to  expel  any  remaining  nitric  acid, 
nnd  redissolved  in  pure  water,  may  be  examined  by  the  appropriate  tests, 
not  for  arsenious  but  for  arsenic  acid. 

For  this  latter  purpose,  the  ammonia-nitrate  of  silver  may  be  used, 
which  gives  with  arsenic  acid  a  brick-red  precipitate. 

Or,  the  arsenic  acid  being  obtained  in  solution,  may  be  precipitated  as 
arseniate  of  lime  by  lime-water,  and  from  this  precipitate  pure. arsenic 
with  its  metallic  lustre  may  be  obtained  by  the  process  next  to  be 
described. 

VII.  Keduction  of  the  Arsenic. — "When  arsenic  is  present  in  any  appre- 
ciable quantity,  it  may  always  be  obtained  in  a  separate  state,  so  as  to 
be  recognised  by  its  peculiar  metallic  lustre  and  garlic  odor  ;   and  no 
chemist  in  any  particular  case  will  positively  swear  to  its  presence  unless 
he  is  able  thus  to  procure  it ! 

For  this  purpose,  provide  a  tube  of  hard  glass,  a  quarter  of  an  inch  in 
diameter  and  three  or  four  inches  long,  with  one  end  hermetically 
sealed;  and  fill  it  to  the  depth  of  half  an  inch  with  a  mixture  of  the 
suspected  substance,  charcoal,  and  carbonate  of  soda,  the  whole  being 
previously  well  dried  at  a  moderate  heat,  and  ground  together  to  a  fine 
powder.  After  wiping  the  inside  of  thfe  tube  with  a  little  cotton  attached 
to  a  wire,  to  remove  any  dust,  or  remaining 
moisture,  a  strong  heat  is  applied  to  the  end 
of  the  tube  containing  the  mixture,  by  whiclrthe 
arsenic  will  be  separated,  to  be  again  condensed 
upon  the  sides  of  the  tube  a  little  above  the 
heated  part.  The  bright  metallic  lustre  will  at 
once  be  recognised,  and  by  breaking  the  tube 
and  heating  the  part  coated,  as  in  the  figure,  the 
peculiar  garlic  odor  will  be  perceived.  Other 
.  tests  may  also  be  applied  to  it  if  desired. 

This  last  test  may  be  applied  to  any  of  the  precipitates  obtained  by 
the  previous  tests. 

QUESTIONS. — Describe  Flandin  and  Danger's  test.  Describe  the  mode 
of  testing  by  reduction  of  the  arsenic.  How  does  the  arsenic  show 
itself?  May  the  last  mode  be  applied  to  the  precipitates  obtained  by 
the  other  modes  ?  • 


CARBON.  257 

296.  In  these  directions  we  are  supposed,  as  a  general  thing,  to  be 
operating  with  pure  ai*senical  solutions,  but  in  cases  of  actual  poisoning 
it  will  usually  be  otherwise  ;  and  it  often  becomes  an  important  object  to 
be  able  to  separate  the  organic  matter  contained  in  the  suspected  sub- 
stance. Sometimes  the  substance  will  be  soluble,  as  sugar,  which  will 
not  interfere  badly  with  the  operation ;  and  at  others  it  will  be  of  such  a 
character  that  it  can  be  removed  by  passing  through  it  a  current  of 
chlorine,  or  it  may  be  that  it  can  be  removed  only  by  heating  it  with 
strong  oil  of  vitriol,  as  heretofore  (VI.)  described.  In  any  particular 
ease,  the  mode  of  proceeding  to  be  pursued  must  be  adapted  to  its 
peculiar  circumstances. 


GROUP  V. 


CARBON  J     Combustible  bodies,  and  incapable  of  being  volatilized  even 
BORON*  N  at  the  hiShest  temperatures. 


CARBON. 
Symbol,  Cj  Equivalent,  6j  Density  (crystdlizecT),  3 "52. 

297.  History. — Carbon,  though  rarely  met  with  in  nature  per- 
fectly pure  and  uncombined,  is  one  of  the  most  important  of  the 
elements,  forming,  as  it  does,  an  essential  ingredient  of  nearly  all 
vegetable  and  animal  bodies.     It  is  found  in  a  variety  of  forms  j 
and  when  uncry^talized   and   uncombined,   its  color  is   always 
bla.ek. 

298.  Preparation  and  Properties. — Carbon  presents  itself  to 
us  in  a  variety  of  forms,  as  the  diamond,  graphite  or  plum~bayot 
mineral  coal,  charcoal,  gas  coal,  and  perhaps  we  may  add  lamp- 
black,  though  the  latter  very  probably  differs  from  charcoal  only 
in  being  in  a  state  of  fine  division. 

QUESTIONS. — 296.  In  these  directions  what  are  we  supposed  to  operate 
with  ?  Will  this  usually  be  the  case  in  practice  ?  Will  it  often  be  neces-' 
eary  to  separate  organic  matters  from  the  suspected  substance  ?  What 
elements  constitute  the  fifth  group?  How  are  they  characterized? 
297.  Give  the  history  of  carbon.  298.  What  are  some  of  the  varieties 
of  carbon  ? 

22* 


258  C  A  U  BON. 

The  diamond  is  pure  crystal ized  carbon,  and  is  the  hardest 
substance  known  in  nature.  The  crystals  are  of  the  form  of  the 
regular  octahedron,  but  the  faces  are  frequently  a 
little  convex,  as  shown  in  the  figure.  Such  crys- 
tals, properly  set,  are  used  for  cutting  glass,  a  pur- 
pose for  which  they  are  admirably  adapted.  Heated 
intensely  in  the  flame  of  the  compound  blowpipe, 
the  diamond  is  entirely  consumed,  forming  carboni 
acid,  just  as  if  the  same  weight  of  pure  charcoal  had  been  con- 
eumed.  Diamonds  are  generally  very  small,  the  largest  ever 
found  weighing  less  than  six  ounces.  A  single  diamond  has 
been  sold  for;more  than  half  a  million  of  dollars.  It  is  generally 
found  in  the  same  situations  as  gold  and  platiaum.  A  few  crys^- 
tals  of  little  value  have  been  discovered  in  the  vicinity  of  the 
gold  mines  in  some  of  the  Soutliern  States.  It  is  a  powerful 
refractor  of  light,  and  seems  to  have  the  faculty  of  absorbing  light, 
and  giving  it  *out  again  after  a 'time.  A  diamond  held  in  the 
sun's  rays  a. few  seconds,  and  then  removed  at  once  to  a  dark 
room,  phosphoresces  very  distinctly  for  a  few  seconds. 

Graphite,  or  plumbago,  called  also,  very  improperly,  black 
lead,  is  a  variety  of  carbon,  containing  usually  a  little  iron.  It 
is  often  found  crystalized  in  thin  scales"  of  a  hexagonal  form.  It 
is  not  unfrequently  formed  as  an  artificial  production  in  iron  fur- 
naces, and  is  sometimes  quite  free  from  iron. 

It  is  used  for  the  manufacture  of  pencils,  and  in  the  con- 
struction of  crucibles  that  are  to  be  exposed  to  a  very  intense 
heat.  For  this  purpose,  it  is  ground  to  a  fine  powder,  and  mixed 
thoroughly  with  fire-clay.  These  crucibles  are  used  chiefly  for 
melting  metals. 

Mineral  coal  is  of  two  kinds.;   the  bituminous,  and  the  non- 
•  bituminous,  or  anthracite. 

Bituminous  coal  is  distinguished  by  its  softening,  like  wax, 
when  heated,  and  giving  on0  much  gas,  which  burns  with  flame.' 

QUESTIONS. — What  is  the  diamond  ?  What  is  said  of  its  hardness  ? 
What  use  is  made  of  it-?  What  is  the  effect  of  the  intense  heat  of  the 
compound  blowpipe  upon  it?  What  is  said  of  the  size  of  diamonds? 
What  is  said  of  the  absorption  of  light  by  the  diamond  ?  What  is 
graphite  or  plumbago  ?  What  use  is  made  of  it  ?  What  two  kinds  of 
mineral  coal  are  there?  How  is  bituminous  coal  distinguished  ? 


CARBON.  259 

It  is  also  much  lighter  than  anthracite,  and  more  easily  ignited. 
Some  of  the  different  varieties  of  bituminous  coal  are  caking, 
splint,  cherry,  and  cannel  coal.  Jet,  also,  which  is  used  in 
jewelry,  is  a  bituminous  coal ;  and  in  the  same  family  may  be 
included  wood  or  Bovcy  coal,  sometimes  called  lignite. 

'  Anthracite,  or  stone-coal,  differs  from  the  above  varieties,  in 
containing  no  bituminous  matter;  and,  therefore,  it  yields  no 
inflammable  gas  by  heat.  Its  sole  combustible  ingredient  is 
carbon ;  and,  consequently,  it  burns  without  flame.  It  is  found 
in  different  countries,  but  nowhere  in  such  profuse  abundance  as 
in  the  eastern  part  of  the  State  of  Pennsylvania,  which  supplies 
most  of  the  northern  and  eastern  parts  of  the  United  States 
with  fuel. 

All  the  varieties  of  mineral  coal  are  believed  to  nave  been 
formed  from  vegetable  substances,  which,  in  the  changes  the 
earth's  surface  has  undergone,  have  become  buried  beneath  it. 

When  bituminous  coal  is  subjected  to  a  high  temperature  in 
close  vessels,*or  with  only  a  limited  supply  of  atmospheric  air, 
the  volatile  or  bituminous  manner  is  expelled,  and  the  remaining 
porous  carbon  is  called  coke.  It  is  used  for  many  important 
purposes  in  the  arts.  » 

Charcoal  is  prepared  by  exposing  vegetable  matter,  and  espe- 
cially wood,  to  a  high  temperature  in  close*  vessels,  or  in  such 
circumstances  as  to  avoid  the  presence  of  atmospheric  air.  By 
the  heat  a  large  quantity  of  water*  acetic  acid,  tar,  and  other 
matters,  is  expelled,  and  the  carbon,  with  any  mineral  matter 
which  has  been  absorbed  from  the  soil,  remains.  The  latter  con- 
stitutes the  ashes  which  remain  after  the  combustion  of  the  coal 
in  the  open  air. 

The  ueual  method  of  preparing  charcoal  for  ordinary  purposes, 
is  to  ignite  large  heaps  of  wood,  which  are  covered  with  earth  so 
as  to  admit  only  a  limited  supply  of  atmospheric  air;  and  the 
result  is  to  char  or  convert  into  coal  a  large  part  of  the  wood,  by 
the  heat  occasioned  by  the  combustion  of  the  other  part. 

QUESTIONS. — What  is  said  of  anthracite  or  stone-coal?  Where  is  it 
found  in  this  country?  What  is  coke?  How  is  charcoal  prepared? 
What  constitutes  the  ashes  ? 


260  CARBON. 

The  figure,  diminished  from  Knapp's  Technology,  represents  a 
section  of  a  coal-pit  ready  to  be  ignited.     The  stake  at  the  centre 


^-  ': 

Preparation  of  Charcoal 

serves  as  a  support  for  beginning  the  heap ;  and  by  one  side  of 
wh^ch  space  is  left  to  kindle  the  fire,  by  dropping  in  pieces  of  very 
dry  wood  and  burning  coals. 

Charcoal  is  a  black,  hard,  brittle  substance,  perfectly  insoluble 
in  every  liquid,  but  attacked  and  oxidized  by  strong  nitric  acid. 
It  is  a  good  conductor  of  electricity,  but-a  non-conductor  of  heat ; 
is  little  acted  upon  by  air  and  moisture,  and  is  perfectly  infusible 
in  the  most  intense  heat  that  can  be  applied  to  it.  Heated  in 
the  open  air,  it  takes  fire  and  burns  freely,  especially  if  in  large 
masses,  leaving  only  a  small  residue  of  ashes. 

299.  Charcoal  possesses  the  property  of  absorbing  a  large 
quantity  of  air,  or  other  gases,  at  common  temperatures,  and 
of  yielding  the  greater  part  of  them  again  when  it  is  heated. 
Recently-burned  charcoal  absorbs  air  and  moisture  so  rapidly,  for 
a  few  days,  as  materially  to  increase  its  weight.  Both  are  absorbed 
and  retained  with.such  force,  that  a  red  heat  is  required  to  expel 
them.  This  absorption  of  air  may  be  readily  shown  in  the  fol- 
lowing manner  : — Let  a  piece  of  charcoal,  of  moderate  size,  be 
heated  to  redness  for  a  few  minutes,  and  then  quenched  under 


QUESTIONS. — Describe  charcoal.     299.  What  is  said  of  the  absorption 
of  gases  by  charcoal  ?     How  may  the  absorption  of  air  bo  shown  ? 


CARBON.  261 

mercury,  and  placed  under  a  receiver,  over  the 
mercurial  cistern.  The  mercury  will  shortly  begin 
to  rise,  in  consequence,  of  the  absorption  of  the  air 
within ;  and  the  process  will  continue  for  several 
hours. 

Charcoal,  likewise,  absorbs  the  odoriferous  and 
coloring  particles  of  most  animal  and  vegetable 
substances.  When  colored  infusions  of  this  kind 
are  digested  with  a  proper  quantity  of  charcoal,  a 
solution  is  obtained  which  is  nearly,  if  not  quite,  colorless. 
Tainted  flesh  may  be  deprived  of  its  odor  by  this  means,  and 
foul  water  be  purified  by  filtration  through  charcoal.  The  sub- 
stance commonly  employed  to  decolorize  fluids  is  animal  charcoal 
reduced  to  a  fine  powder.  It  loses  the  property  of  ^absorbing 
coloring  matters  by  use,  but  partially  recovers  it  by  being  heated 
to  redness. 

At  very  high  temperatures  charcoal  has  a  higher  affinity  for 
oxygen  than  any  other  substance,  and  is  therefore  often  heated 
with  oxides  of  the  metals  to  deoxidize  them,  or  deprive  them  of 
their  oxygen. 

Lampblack  is  minutely  divided  carbon,  prepared  by  burning 
rosin  or  tar  in  a  confined  portion  of  air,  so  that  the  hydrogen 
only  of  the  material  is  consumed,  and  the  carbon  remains  as  an 
exceedingly  fine  powder.  It  is  used  as  a  pigment,  and  for  other 
purposes. 

Gas  coal -is  a  deposite  of  nearly  pure  carbon  upon  the  inside 
of  the  large  retorts  used  in  the  manufacture  of  illuminating  gas. 
It  is  very  hard  and  black,  and  a  good  conductor  of  electricity. 

Uses. — Carbon  is  used  as  fuel;  in  forming  gunpowder;  as' a 
pigment)  in  the  formation  of  steel;  as  a*  polishing-powder ;  and 
in  medicine  as  an  antiseptic,  &c.,  &c. 

QUESTIONS. — What  is  said  of  the  affinity  of  charcoal  for  oxygen  at  high 
temperatures  ?  What  is  lampblack  ?  What  use  is  made  of  it  ?  What  is 
gas  coal  ? 


262  COMPOUNDS   OP  CARBON  AND  OXYGEN. 


Compounds  of  Carbon  and  Oxygen. 

300.  Carbon  combines  with  oxygen  in  two  proportions,  form- 
ing carbonic  oxide,  CO,  and  carbonic  acid,  C02. 

301.  Carbonic  Oxide,  Protoxide  of  Carbon— CO;  eq.,  (6  +  8=-)  14.— 
This  is  a  gaseous  substance,  and  is  best  prepared  by  heating  a  mixture 
of  equal  parts  of  dry  powdered  chalk  and  iron-filings  in  a  gun-barrel. 
The  chalk,  which  is  carbonate  of  lime,  when  heated,  gives  off  its  carbonic 
acid  (the  compound  next  to  be  described)  in  contact  with  the  heated  iron, 
by  which  one-half  of  its  oxygen  is  instantly  absorbed,  and  the  carbonic 
oxide  thus  produced  passes  on,  and  may  be  collected  over  water.     Thus, 

CaO,C02  -f  Fe  =  CaO  -f  FeO  -f  CO. 

Another  method  of  preparing  it,  is  to  heat  gently  a  mixture  of  oxalic 
acid  and  five  or  six  times  its  weight  of  oil  of  vitriol,  by  which  both  car- 
bonic oxide  and  carbonic  acid  are  produced  in  equal  volumes ;  but  the 


Preparation  of  CO. 

latter  may  readily  be  separated  by  passing  it  through  a  solution  of  caustic 
potash  or  milk  of  lime,  in  the  three-necked  bottle,  and  collected  over 
water.  The  changes  which  take  place  are  as  follows,  viz : — 

• 
C203,3HO  +  S03,HO  =  S03,4HO  -f  C02  -f  CO. 

The  density  of  the  gas  is  about  0-97;  100  cubic  inches  weighing  30-20 
grains.  It  is  highly  combustible,  and  burns  with  a  beautiful  blue  flame. 

QUESTIONS. — SOO.^What  compounds  of  carbon  and  oxygen  are  there? 
301.  Describe  the  mode  first  mentioned  for  preparing  carbonic  oxide. 
The  second  mode.  Is  carbonic  oxide  combustible  ?  What  is  the  color 
of  the  flame  ?  •  •  / 


COMPOUNDS   OF   CARBON   AND   OXYGEN. 


263 


It  will  not  support  respiration  or  combustion ;  and 
a  lighted  candle  being  immersed  in  it,  as  heretofore 
described  in  connection  with  hydrogen  (198),  is  in- 
stantly extinguished. 

It  is  this  gas  which  gives  the  blue  flame  seen 
about  the  fire  of  the  blacksmith,  and  in  anthracite 
stoves,  when  the  door  is  suddenly  opened  soon  after 
the  fire  has  been  kindled,  and  in  furnaces  for  the 
reduction  of  the  metals  from  their  ores. 

Carbonic  oxide  is  believed  to  be  composed  of  1  vol. 
of  carbon  vapor  and  1  vol.  of  oxygen  combined  with- 
out condensation.  '  Thus, 

1  vol.  of  carbon  vapor  weighs      -836 
1  vol.  of  oxygen  "        1-106 


2  vols.  of  carbonic  oxide     " 
1  vol.  of  the  oxide  therefore  " 


1-942 
•971 


CO  is  Combustible. 


302.  Carbonic  Acid— C02;  eq.,  (6  +  16  =)  22.  —  Carbonic 
acid  is  remarkable  as  being  the  first  gaseous  substance  recognise'd, 
after  atmospheric  air,  which  must  always  have  been  known.  It 
was  first  described  by  Dr.  Black,  in  1757,  and  called,  by  him, 
fixed  air,  because  he  found  it  fixed  in 
common  limestone  and  magnesia;  from 
which  it  may  be  expelled  by  heat,  or 
by  the  action  of  any  strong  acid.  It 
may  be  collected  over  water,  but  a  por- 
tion will  be  absorbed.  A  gas-bottle,, 
of  the  form  shown  in  the  figure,  is  con- 
venient for  preparing  it.  Some  frag- 
ments of  marble,  and  water,  are  placed 
in  the  bottle,  and  the  cover  put  on,  Preparation  of  co». 

and  then  strong  hydrochloric  acid  is  poured  into,  the  long-necked 
funnel. 

As  thus  prepared,  carbonic  acid  is  a  colorless,  inodorous  gas, 
of  specific  gravity  1-52;  100  cubic  inches  weighing  47-14  grains. 

It  is  considered  a  compound  of  1  vol.  of  carbon  vapor  and  2  vols.  of 
oxygen  condensed  to  2  vols.     Thus, 


QUESTIONS. — 302.  When  was  carbonic  acid  discovered  ?  What  was  it 
first  caUed?  How  may  it  be  prepared ?  What  is  its  specific  gravity? 
What  is  it  composed  of? 


264 


COMPOUNDS   OF   CARBON   AND   OXYOElf. 


1  vol.  of  carbon  vapor  weighs  *836 

2  vols.  of  oxygen.  "      (1-106  X  2)  2-212 

2  vols.  of  carbonic  acid   "  3-048 

The  weight  of  1  vol.  therefore  is  1-524 

Or  we  may  consider  it  a  compound  of  2  vols.  of  carbonic  oxide  and  1 
vol.  of  oxygen,  condensed  to  2  vols.,  as  follows : 

2  vols.  of  carbonic  oxide  weigh  (-971  X  2)  1-942 
1  vol.  of  oxygen  "  1-106 

Giving  for  the  weight  of  2  vols.  of  C02,          3  -048 
And  for  the  weight  of  1  vol.,  as  before,  1-524 

Carbonic  acid  is  so  much  heavier  than  atmospheric  air,  that 
it  may  be  poured  from  one  vessel  to  another  without  difficulty. 

Let  a  bottle,  with  a  wide  mouth,  be 
filled  with  the  gas,  and  then  plunge 
into  it  a  piece  of  lighted  paper,  or 
other  substance,  so  that  some  smoke 
may  be  mixed  with  it  and  render  its 
motions  visible.  Then  hold  the  bottle 
in  the  hand,  as  if  pouring  a  liquid  from 
it  (as  represented  in  the  figure),  and  the  motion  of  the  gas,  as  it 
is  emptied  from  it,  will  be  made  apparent  to  the  eye. 

Another  instructive  experiment  of  the  same  character  may  be 

performed  as  follows  :  Provide 
a  glass  jar  with  a  large  mouth, 
and  place  at  the  bottom  a  lighted 
taper,  as  shown  in  the  figure. 
Then  having  filled  another  jar 
of  about  equal  capacity  with 
carbonic  acid  gas,  carefully  re- 
move the  cover  and  gradually 

pour  the    Contents    into   the  first- 
Candle  Extinguished,  mentioned    jar; — the    flame    of 
the  taper  will  first  be  considerably  disturbed  by  the  motion  occa- 
sioned by  the  descending  gas,  and  will  finally  be  extinguished. 

QUESTIONS. — How  may  the  high  specific  gravity  of  carbonic  acid  be 
shown  by  pouring  it  from  a  vessel  ?  How  may  the  flame  of  a  candle  be 
extinguished  by  it  ? 


C0a  poured  from  a  Vial. 


COMPOUNDS   OF   CARBON   AND   OXYGEN. 


265 


By  a  pressure  of  36  atmospheres,  at  32°,  it  is  converted  into  a 
beautiful  transparent  liquid,  which  may  be  frozen  by  intense  cold, 
in  the  manner  already  explained. 

303.  It  is  capable  of  supporting  neither  combustion  nor  respira- 
tion;— a  burning  candle  plunged  into  it  is  instantly  extinguished  ;  - 
and  a  living  animal,  thrown   into  a  vessel  containing  it,  even    » 
though  considerably  diluted  with  air,  soon  dies.     Carbonic  acid 

is  always  produced  by  ordinary  combustion  j  and  lives  have  often 
been  lost  by  persons  placing  an  open  dish  of  burning  charcoal  in 
their  bed-rooms  before  retiring  to  rest.  The  oxygen  of  the  air  in 
the  room  is  taken  up  by  the  carbon,  and  the  gas  in  question  takes 
its  place,  producing  the  effects  described.  It  is  produced,  also, 
by  the  decay  of  animal  and  vegetable 
substances,'  and  sometimes  is  found 
collected  in  caves  and  wells,  and  is 
called  choke-damp. 

Though  this  gas  does  not  support  com- 
bustion, as  the  experiment  is  ordinarily 
made,  yet  potassium,  sodium,  and  some 
other  of  the  metals  may  be  made  to  burn 
in  it.  For  this  purpose,  fill  a  flask  with 
dry  carbonic  acid  gas,  and  drop  into  it  a 
small  piece  of  potassium,  and  apply  the 
heat  of  a  lamp  at  the  point  where  the 
metal  lies,  by  means  of  a  blowpipe.  When 
it  has  become  very  hot  the  metal  takes  fire 
and  burns  brilliantly,  the  carbon  of  the 
carbonic  acid  decomposed  being  deposited 
upon  it  as  a  black  powder.  Combustion  of  Potassium  iu  COa. 

304.  Soda-fountains  are  formed  by  compressing  a  large  quantity 
of  this  gas  in  water,  contained  in  a  strong  vessel  adapted  to  the 
purpose.     When  the  tube  leading  from  the  fountain  is  opened, 
the  water  "is  forced  out  by  the  pressure,  and  effervesces  violently 
by  the  escape  of  the  gas.     Soda-powders,  &c.,  often  used  to  pro- 
duce an  agreeable  drink,  in  the  absence  of  a  soda-fountain,  consist 
of -bicarbonate  of  soda  and  tartaric  acid,  which,  when   mingled 

QVESTIONS. — May  carbonic  acid  be  compressed  to  the  liquid  form? 
303.   Is  it  always  produced  in  ordinary  combustion  ?     How  may  potas- 
sium bo  made  to  burn  in  it  ?    What  becomes  of  the  carbon  of  the  carbonio 
acid  ?    304.  How  are  soda-fountains  formed  ? 
23 


266 


COMPOUNDS   OP.  CARBON    AND    HYDROGEN. 


together  in  solution,  produce,  by  chemical  action,  tartrate  of  soda, 
the  carbonic  acid  passing  off  into  the  air  with  effervescence.  So, 
also,  the  effervescence  which  takes  place  on  opening  a  bottle  of 
beer,  cider,  or  champagne  wine,  is  owing  to  the  escape  of  this 
gas,  which  has  been  produced  by  the  fermentation  of  the  liquid. 
All  kinds  of  spring  and  well-water  contain,  it  in  small  quantity, 
and  become  insipid  to  the  taste  by  boiling,  in  consequence  of  the 
gas  having  been  expelled.  It  is  also  always  present  in  the  atmo- 
sphere, and  in  some  cases  accumulates  in  considerable  quantities, 
as  at  the  Grotto  del  Cane,  in  Italy,  through  which  a  man  may 
pass  without  danger,  but  a  dog  on  entering  it  is  instantly  suffo- 
cated. The  carbonic  acid  here  constantly  issues  from  the  earth, 
and  accumulates  at  the  bottom,  while  the  air  above  remains  com- 
paratively pure. 


305.  Lime-water  is  an  excellent  test  for 
carbonic  acid;  and  a  vessel  of  it  being  al- 
lowed to  stand  a  few  hours,  becomes  coated 
with  a  pellicle  of  carbonate  of  lime,  by  ab- 
sorbing t  this  gas  from  the  air.  So  lime-water 
becomes  milky  by  blowing  into  it  with  a  tube 
from  the  lungs,  for  the  same  reason.  A  por- 
tion of  the  lime  is  changed  into  carbonate  of 
lime,  which  is  insoluble,  and  gives  the  water  its 
milkiness. 


Blowing  through 
Lime-water. 


Compounds  of  Carbon  and  Hydrogen. 

306.  Carbon  and  hydrogen  combine  in  a  number  of  different 
proportions,  producing  compounds,  several  of  which  are  of  special 
interest,  because  of  their  isomeric  character;  but  we  shall  here 
describe  only  two,  both  of  which  are  gaseous,  viz.,  light  carbu- 
retted  hydrogen,  C2H4,  and  olefiant  gas,  C4H4. 


QUESTIONS. — What  is  said  of  the  Grotto  del  Cane  in  Italy  ?  305.  How 
is  lime-water  affected  by  blowing  through  it  with  the  mouth?  Give 
the  reason  for  the  milkiness  produced  ?  300.  What  is  said  of  the  com- 
pounds of  carbon  and  hydrogen  ? 


COMPOUNDS  OP  CARBON  AND  HYDROGEN.       267 

807.  Light  Carburetted  Hydrogen—  C2H4;  eq.,  (12  +  4=) 
16.  —  This  gas,  called  also  fire-damp,  marsh  gas,  hydrocarburet,  and 
dicarburet  of  hydrogen,  is  formed 
by  the  slow  decomposition  of  wood, 
and  woody  substances,  under  water,' 
especially  in  warm  weather;  and 
may  be  obtained  by  stirring  the 
mud  and  other  mattery  at  the  bot- 
tom of  stagnant  pools  (see  figure), 

and  collecting  the  bubbles  of  gas  in  Collecting  Marsh  Gas. 

a  receiver,  as  they  rise.      It  some- 

times accumulates  in  large  quantities  in  coal  mines,  where  it  is 
formed  by  the  action  of  water  upon  the  coal. 

It  is  bests  prepared  by  heating  in  a  flask,  made  of  hard  glass,  a 
mixture  of  2  parts  of  acetate  of  soda,  3  parts  of  caustic  potash, 
and  3  of  quick-lime.  The  composition  of  the  acetic  acid  is 
C4H404,  which,  it  will  be  perceived,  is  precisely  equal  to  2  eq. 
of  carbonic  acid,  and  1  of  the  hydrocarburet  in  question.  Thus, 


The  use  of  the  lime  is  to  protect  the  gas  from  the  action  of  the 
potash. 

Light  carburetted  hydrogen  is  a  colorless,  transparent  gas,  100 
cubic  inches  of  which  weigh  17*37  grains,  giving  it  a  specific 
gravity  of  0-56. 

One  volume  contains  2  vols,.  of  hydrogen,  J  of  a  vol.  of  carbon  vapor. 
Thus, 

2  vols.  of  hydrogen  weigh  (-069  x  2)  -138 
\  vol.  vapor  of  carbon  (-1L6)  -418 

-     .    1  vol.  of  the  hydrocarburet,  -556 

A  burning,  candle  is  extinguished  by  it,  but  it  is,  itself,  highly 
combustible,  and  burns  with  a  feeble,  yellow  flame.  Mixed  with 
twice  its  own  volume  of  oxygen,  or  seven  or  eight  times  its  volume 

QUESTIONS'.  —  307.  In  what  situations  is  light  carburetted  hydrogen 
naturally  formed?  How  may  it  be  collected?  How  may  it  be  prepared 
artificially  ? 


268  COMPOUNDS   OF   CARBON   AND    HYDROGEN. 

of  air,  it  explodes  violently  by  the  electric  spark,  or  on  the  ap- 
proach of  flame. 

308.  defiant  Gas,  or  Heavy  Carburetted  Hydrogen— C4H<; 

eq.,  (24  +  4=)  28.— This  gas  was  first  described  in  1796,  by 
some  Dutch  chemists,  who  gave  it  the  name,  defiant  gas,  because 
of  its  forming  with  chlorine  a  peculiar  oil-like  liquid.  It  is  color- 
less and  tasteless,  and  but  slightly  absorbed  by  water;  100  cubic 
inches  weigh  3041  grains,  so  that  its  density  is  0-98. 

Its  volume  contains  2  vols.  of  hydrogen,  and  1  vol.  of  vapor  of  carbon, 
as  follows : 

2  vols.  of  hydrogen  weigh  (-069  x  2)  -138 
1  vol.  of  vapor  of  carbon,  -830 

Giving  for  1  vol.  of  olefiant  gas,  -974 

Olefiant  gas  is  prepared  by  mixing,  in  a  capacious  retort,  one 
part  of  alcohol  with  four  of  concentrated  sulphuric  acid,  and 
heating  the  mixture,  as  soon  as  it  is  made,  by  means  of  a  lamp 
or  ignited  charcoal.  The  acid  soon  acts  upon  the  alcohol,  effer- 
vescence ensues,  and  olefiant  gas  passes  over,  mixed  with  other 
substances,  chiefly  sulphurous  acid,  from  which  it  may  be  purified 


Preparation  of  Olefiant  Gas. 


by  washing  it  with  solution  of  lime  or  caustic  potassa  in  several 
of  Woulf  s  bottles,  as  shown  in  the  figure. 

As  might  be  expected,  olefiant  gas  does  not  support  com- 
bustion ;  but  a  jet  of  it  burns  in  the  air,  or  in  oxygen  gas,  with  a 

QUESTIONS. — Does  light  carburetted  hydrogen  form  explosive  mixtures 
•with  oxygen  or  atmospheric  air  ?  308.  By  whom  was  olefiant  gas  dis- 
covered? Why  was  it  so  called?  Describe  it.  How  is  it  prepared? 
What  is  said  of  the  light  produced  by  its  combustion  ? 


COMPOUNDS  OF  CARBON  AND  HYDROGEN.       269 

brilliant  white  light.     Mixed  with  oxygen,  or  air,  in  proper  pro- 
portions, it  explodes  violently,  like  the  preceding  compound. 

309,  liluminating  Gas  is  usually  a  mixture  of  olefiant  and 
light  carburetted  hydrogen  gases,  and  is  formed  by  distilling,  in 
large  cast-iron  retorts,  rosin,  tar,  or  other  resinous  or  oily  sub- 
stances, or  bituminous  coal.     Besides  the  gases  mentioned,  there 
are  also  formed  other  hydro-carbons,  but  in  less  quantity.     Illumi- 
nating gas  is  used  in  imtnense  quantities  in  large  cities,  for  lighting 
the  streets,  and  for  fixed  lights  in  stores  and  other  buildings. 

Illuminating  gas  is  now  chiefly  prepared  from  bituminous  coal, 
and  as  it  passes  from  the  retorts  is  mixed  with  tar,  carbonic  acid, 
sulphuretted  hydrogen,  salts  of  ammonia,  and  other  matters,  from 
which  it  must  be  freed  before  being  admitted  to  the  burners.  For 
this  purpose,  it  is  washed  by  passing  it  through  water,  and  then 
further  purified  by  passing  through  vats  containing  recently- 
slaked  lime. 

If  this  gas  is  made  to  pass  through  a  heated  tube  it  is  decom- 
posed, and  a  part  of  its  carbon  is  deposited  as  a  coating  upon  the 
inside  of  the  tube.  In  this  way  large  deposits  of  jftire  carbon 
are  often  formed  in  the  retorts  of  gas-works.  It  has  been  de- 
scribed above  (299)  as  gas  carbon. 

310.  The  History  of  gas  manufacture,  for  illuminating  purposes,  pos- 
sesses much  interest,  as  showing  the  great  benefit  conferred  by  science  on 
the  arts,  and  domestic  and  public  economy.     In  1680,  Mr.  Clayton,  of 
Yorkshire,  England,   observed  that  a   brilliant  light  -was  produced  by 
igniting  the  gas  which  issued  from  a  close  vessel  containing  bituminous 
coal  when  heated,  but  it  was  a  century  after  this  before  any  direct 
experiments  were  made  with  it,  with  reference  to  its  use  in  the  arts.     In 
1785,  the  preparation  of  gas  for  illumination,  from  the  destructive  distil- 
lation of  wood,  was  suggested ;  but,  in  1792,  some  buildings  were  actually 
illuminated  .with  gas,  in  Cornwall,  England;   and  the  same  thing  was 
repeated  in  1798,  at  a  foundry  in  Birmingham.     In  1805,  some  of  the 
cotton-milJs  in  Manchester  were  first  lighted  with  gas,  by  means  of 
permanent  fixtures,  prepared  for  the  purpose;   and  this  date  may  be 
assumed  as  the  beginning  of  the  use  of  gas-lights  for  practical  purposes. 
In  a  half  century,  therefore,  has  this  manufacture  attained  its  present 
importance ;  and  the  time  is  not  distant  when  the  quantity  annually  con- 
sumed in  every  civilized  country  will  be  greatly  increased.  • 

QUESTIONS. — 809.  What  is  illuminating  gas  ?     How  is  it  usually  pre- 
pared?     What  is  the  substance  now  generally  used  for  producing  it' 
310.  What  is  said  of  the  history  of  the  use  of  illuminating  gas  for  prac- 
tical purposes  ? 
23* 


270  NATURE   OP   FLAME. — THE    SAFETY   LAMP. 


Nature  of  Flame.—  The  Safety  Lamp. 

311.  What  we  term  the  combustion  of  a  substance  is  occasioned 
by  its  entering  into  combination  with  some  other  substance,  usually 
the  oxygon  of  the  atmosphere,  and  then  taking  another  form  as  a 
compound  (193).  Of  the  two  substances  thus  required  to  produce 
combustion,  one  is  called  the  combustible  substance,  and  the  other 
the  supporter  of  the  combustion  ;  but  the  action  is  really  mutual 
between  them,  and  neither  can  burn  without  the  other.  The 
supporter  of  ordinary  combustion,  oxygen,  is  always  gaseous,  but 
the  combustible  may  be  either  solid,  liquid,  or  gaseous. 

Flame  is  gaseous  matter  in  a  state  of  combustion,  and  is  made 
incandescent  by  the  intense  heat  of  the  combustion.  Two  gases 
are  needed  to  produce  it,  one  of  which  must  be  combustible,  and 
the  other,  of  course,  a  supporter  of  combustion.  The  action  is 
mutual  between  them  ;-  —  neither  will  burn  alone  ;—  and  a  jet  of 
either  will  burn  in  the  other. 

In  the  common  lamp  or  candle,  the  combustible  gases  are  sup- 
plied from  the  oil,  or  tallow,  which  is  gradually  raised,  by  <;he 
capillary  action  of  the  wick,  into  the  flame,  where  it  is  decom- 
posed by  the  heat.  As  these  gases,  thus  produced,  escape  from 
the  wick,  and  come  in  contact  with  the  oxygen  of  the  atmosphere, 
the  two  combine,  producing  the  phenomena  of  light  and  heat,  with 
which  all  are  familiar.  A  careful  inspection  of  the  flame  of  a 
lamp  or  candle,  as  it  burns  quietly,  will  show,  that  it 
is  composed  of  three  parts,  viz  :  —  1st,  a  central  part,  a, 
surrounding  the  wick,  and  extending  a  little  above  it, 
of  gaseous  matter  that  has  emerged  from  the  wick,  and 
is  making  its  way  outward  to  the  atmosphere,  which  it 
has  not  yet  reached,  and  therefore  has  not  yet  become 
ignited;  2d,  the  bright  part  of  the  flame,  bb,  which, 
in  the  form  of  a  conical  shell,  incloses  the  part  a,  and 
Iliil  I  iiil'i'i  consists  of  gaseous  matter  in  a  state  of  rapid  combustion, 
the  combustible  particles,  as  they  reach  the  air,  uniting 


QUESTIONS.  —  311.  What  is  ordinarily  termed  combustion?  Must  there 
be  two  substances  to  produce  combustion  ?  What  are  they  called  ?  What 
is  flame?  In  the  common  lamp  or  candle,  how  are  the  combustible  gases 
supplied  ?  Of  what  several  parts  is  the  flame  of  a  candle  composed  ?  What 
is  the  dark  interior  part  ? 


NATURE   OF   FLAME. — THE    SAFETY   LAMP. 


271 


with  its  oxygen,  with  the  evolution  of  much  light  and  heat ;  and, 
3d,  the  part,  cc,  outside  of  the  part  last  mentioned,  composed 
chiefly  of  heated  air,  and  mixed  with  a  small  portion  of  com« 
bustible  matter  in  a  state  of  ignition. 

That  the  dark,  interior  portion,  a,  is  composed  of  combustible 
gas,  may  be  shown  by  inserting,  in  the  , 
centre  of  the  flame,  one  end  of  a  small 
glass  tube,  as  shown  in  the 'figure,  and 
conveying  away  a  portion,  and  igniting  it  • 
as  it  escapes  at  the  other  end.     So,  when 
the  flame  of  a  candle  is  suddenly  extin- 
guished, the  heat  in  the  wick  continues, 
for  a  short  time,  sufficient  to  decompose 

the    tallow,    and    the     combustible     gases      Gas'Trom  centre  of  Flame. 

continue  to  rise  in  the  form  of  smoke ; 

and  may  often  be  again  relighted  by  applying  the  flame  of  another 

candle  to  the  ascending  smoke,  several  inches  above  the  wick. 

In  the  flame  of  a  jet  of  gas,  precisely  the  same  phenomena,  in 
every  particular,  will  be  observed; — the  dark  central  cone  of 
unconsumed  gas,  surrounded  by  the  brilliant 
hollow  cone  of  flame,  and  this  enveloped  in 
still  another  less  brilliant  cone.  In  the  latter 
case,  the  gas  is  previously  formed  and  consumed 
as  it  issues  into  the  air,  but  in  the  case  of  the 
candle  or  lamp,  it  is  formed  in  the  wick,  and 
instantly  consumed  as  it  escapes. 

312.  That  there  is  really  no  combustion  in 
the  dark  central  part  of  the  flame,  appears  from 
the  fact  that  the  wick  remains  there  uncon- 
sumed, and  is  even  protected  by  the  gas  existing 
there  from  being  attacked  by  the  oxygen  of 
the  air.  In  burning  ordinary  tallow  candles, 
the  wick  occasionally  becomes  too  long,  and  requires  to  be  snuffed 
but  the  wicks  of  the  best  spermaceti  and  wax  candles,  being  plaited, 

QUESTIONS. — How  may  the  real  character  of  this  gas  be  shown  ?  Will 
the  same  phenomena  be  shown  in  the  flame  of  a  jet  of  gas?  312.  Why 
does  not  the  wick  of  a  candle  burn  off  quite  down  to  the  tallow  ? 


Effect  of  Braided 
Wick. 


272  NATURE   OF   FLAME. — THE   SAFETY   LAMP. 

the  end  curls  outward  when  heated  by  the  flame,  and  coming  in 
contact  with  the  oxygen  of  the  air,  is  gradually  consumed  as  the 
candle  burns  away.  The  necessity  of  snuffing  is  therefore 
avoided. 

The  plaited  or  braided  wick,  while  the  candle  is  burning, 
will  always  bend  toward  that  side  in  which 
the  direction  of  the  separate  strands  is  upward 
and  inward,  and  of  course  from  the  other  side 
in  which  the  direction  is  upward  and  outward, 
Generally  the  simple  braiding  of  the  wick  is 
sufficient,  but  sometimes  a  cord  or  bobbin  is 
braided  in  with  one  of  the  strands,  as  repre- 
sented in  one  of  the  figures  in  the  margin  ;  and 
sometimes,  also,  a  cord  is  bound  to  the  braided 

Braided  Wicks.  «..-.« 

wick,  by  a  thread  wound  spirally  around  it. 

The  intensity  of  the  light  from  any  flame,  other  things  being 
equal,  will  depend  upon  the  intensity  of  the  combustion,  and  this 
will  depend  in  turn  upon  the  regular  and  abundant  supply  of  the 
combustible  and  the  supporter.-  When  the  wick  of  a  candle 
becomes  too  long,  or  that  of  a  lamp  is  too  high,  only  the  hydrogen 
of  the  gases  formed  from  the  decomposed  oil  is  consumed,  the 
carbon  escapes  in  a  finely  divided  state,  as  a  dense,  black  smoke. 
This  is  because  of  the  too  rapid  supply  of  the  combustible,  and 
the  usual  remedy  is  to  diminish  the  length  of  the  wick  by  snuf- 
fing or  otherwise,  but  .the  same  thing  would  be  accomplished  by 
increasing  the  supply  of  the  supporter,  oxygen.  This  last  pur- 
pose is  effected  by  the  use  of  a  glass  chimney,  by  which  a  current 
of  air  is  supplied  more  rapidly  to  the  flame. 

By  the  Argand  burner  (so  named  from  the  inventor),  a  cur- 
rent of  air  is  also  supplied  to  the  centre  of  the  flame,  the  wick 
being  in  the  form  of  a  hollow  cylinder,  as  shown  in  the  figure  on 
next  page.  Both  through  the  centre  of  the  flame  and  around 

QUESTIONS. — How  are  the  wicks  sometimes  made  to  bend  outward  in 
th«  air,  so  that  the  end  is  consumed  ?  Upon  what  will  the  intensity  of  the 
light  from  a  flame  depend?  What  occasions  the  disagreeable  smoke 
sometimes  produced  by  a  lamp  ?  How  is  the  defect  usually  remedied  ? 
What  is  the  benefit  of  a  chimney  to  a  lamp  ?  Why .  are  hollow  wicks 
often  used  ? . 


NATURE   OF   FLAME. —  THE   SAFETY  LAMP. 


273 


the  outside  strong  currents  of  air  are  esta- 
blished, as  shown  by  the  arrows.  The 
effect  is  to  produce  a  perfect  combustion 
of  all  the  oil  or  other  combustible  material 
supplied  to  the  flame. 

It  is  found  that  the  intensity  of  light 
produced  by  a  flame  depends  very  much 
upon  the  amount"  of  carbon  consumed. 
The  flame  of  pure  hydrogen  is  very  feeble, 
as  is  also  that  of  the  vapor  of  alcohol  and 
ether ; — and  these  latter  contain  compara- 
tively little  carbon.  But  add  to  alcohol 
one-fourth  of  its  volume  of  camphene, 
which  is  rich  in  carbon,  and  a  brilliant 
flame  is  produced.  This  mixture  con- 
stitutes the  common  burning  fluid. 


Lamp  with  Hollow  Wick  and 
Glass  Chimney. 


Use  of  Blowpipe. 


313,  The  llowpipe  (193)  is,  as  we  have  seen,  simply  a  con- 
trivance to  supply  air  to  the  flame 

from  the  lungs.  The  instrument  is 
usually  applied  to  one  side  of  the 
flame,  and  as  the  current  of  air  is 
forced  through  it,  it  is  bent  towards 
the  opposite  side.  By  means  of  this 
instrument  a  very  intense  heat  may 
be  produced,  sufficient  for  many  im- 
portant purposes.  '  Much  will  depend 
in  any  particular  case  upon  the  mode  of  using  the  flame ;  and  the 
inexperienced  student,  before  commencing,  will  consult  works 
that  treat  at  length  of  this  subject. 

314.  Safety-Lamp. — The  safety-lamp  is  the  invention  of  Sir 
M.  Davy,  to  avoid  the  danger  of  explosions  from  mixtures  of  the 
above  gases  with  air,  which  often  occur  in  coal  mines,   when 
unprotected  lamps  are  made  use  of.     It  consists  simply  of  a  com- 

QUESTIONS. — What  is  the  composition  of  burning  fluid?  313.  Describe 
the  mouth  blowpipe.  May  a  very  intense  heat  be  produced  by  it? 
314.  For  what  special  purpose  was  the  safety-lamp  invented? 


274 


NATURE   OF   FLAME. —  THE   SAFETY   LAMP. 


Safety-Lamp. 


mon  lamp,  the  flame  of  which  is  surrounded  by 
wire  gauze,  through  which,  it  is  found,  flame  will 
not  ordinarily  pass.  This  lamp,  as  it  is  usually 
constructed,  is  represented  in  the  figure  on  the 
left.  Its  action  in  arresting  flame  is  easily  under- 
stood when  the  nature  of  flame  is  considered.  We 
have  seen  that  this  is  simply  gaseous  matter  in  a 
state  of  combustion,  and  therefore  is  intensely 
heated; — now  if  by  any  means  we  can  diminish 
the  heat  of  this  gaseous  matter,  so  that  it  shall  fall 
below  the  point  of  ignition,  the  combustion,  and 
consequently  the  flame,  must  cease.  And  this 
effect  is  produced  by  the  wire  gauze. 

To  show  the  effect, 

let  a   piece   of  such 

gauze,  &,  be  held  in 

the  flame  of  a  candle, 

a-f  the  flame  appears 
to  be  cut  off  by  the  gauze,  and  the 
gases  pass  through  unconsumed,  as 
shown  at  d,  and,  by  dexterous 
management,  may  be  relighted. 

The  occurrence  of  combustible  gases  in  coal  mines  is  occasioned 
by  the  action  of  water  upon  the  coal ;  and  they  often  collect  in 
large  quantities  in  places  not  -properly  ventilated,  forming  mix- 
tures with  the  air,  ready  to  explode  with  excessive  violence  on  the 
first  approach  of  the  unprotected  candle  of  the  miner.  Before  the 
invention  of  the  safety-lamp,  such  accidents  were  of  frequent 
occurrence ;  and  coal  miners  lived  and  worked  in  .perpetual  fear ! 
All  this  is  avoided  by  the  use  of  the  safety-lamp  j — and,  in  view 
of  what  has  been  said  above,  the  mode  in  which  it  operates  to 
afford  the  desired  protection  is  easily  understood.  When  this 

QUESTIONS. — Describe  the  safety-lamp.  What  is  flame?  Will  ordi- 
nary flame  pass  through  wire  gauze  ?  What  is  the  reason  given  for  this 
fact  ?  How  may  this  be  shown  by  a  lighted  candle  and  a  piece  o£  wire 
gauze  ?  How  are  inflammable  gases  formed  in  coal  mines  ?  What  is  the 
effect  when  these  gases,  mixed  with  atmospheric  air,  come  in  contact 
with  -the  flame  of  a  lamp  ?  What  is  the  effect  when  the  safety-lamp  is 
used? 


Effect  of  Wire  Gauze. 


COMPOUNDS   OP   CARBON   AND    NITROGEN.  275 

lamp  is  carried  into  an  atmosphere  containing  a  considerable  pro- 
portion of  fire-damp,  this  latter  immediately  takes  fire,  and  burns 
freely  within  the  gauze,  but  the  flame  is  not  communicated  to  that 
without.  At  first,  the  flame  of  the  lamp  seems  to  be  simply  en- 
larged, but  soon  it  leaves  the  wick  entirely,  and  the  whole  space 
immediately  inside  the  gauze  seems  filled  with  flame.  When 
this  takes  place,  the  miner  is  obliged  to  retire,  lest,  by  the  intense 
heat,  the  wire  of  the  gauze  should  be  melted  or  oxydized,  and 
the  flame  communicated  to  the  mixed  gases,  without.  The  same 
effect  might  also  be  produced  by  strong  currents  of  air,  which 
sometimes  occur,  forcing  the  concentrated  flame  against  a  particular 
part  of  the  gauze,  and  causing  it  to  break,  or  heating  it  so  as  to 
allow  the  passage  of  flame  through  it. 

The  mode  in  which  the  safety-lamp  t>per£tes  may  be  shown  quite  well, 
by  pouring  a  little  sulphuric  ether  into  a  common  glass  receiver,  which 
should  be  inverted  and  agitated  a  little,  so  that  it  may  be  filled  with  a 
mixture  of  air  and  vapor  of  ether,  and  then  letting  the  lighted  lamp 
down  into  it.  The  mixture  of  air  and  vapor  of  ether  entering  through 
the  gauze,  burns  brilliantly  within  the  gauze,  but  the  flame  is  not  com- 
municated to  that  without. 

It  should  be  remarked,  that  wire  gauze  serves  as  a  protection  a'gainst 
explosive  mixtures  of  atmospheric  air  and  the  carburetted  hydrogen  only; 
a  mixture  of  atmospheric  air  or  oxygen  with  pure  hydrogen  may  be  ex- 
ploded through  a  very  narrow  tube  of  great  length. 


Compounds  of  Carbon  and  Nitrogen. 

315.  There  are  several  compounds  of  these  two  substances,  but 
we  shall  notice  only  one,  the  bicarbonide  of  nitrogen,  C2N,  or 
cyanogen  (from  kuanos,  blue,  and  gennao,  to  produce,  because  it 
is  an  ingredient  of  Prussian  blue). 

316.  Bicarbonide  of  Nitrogen,  or  Cyanogen — C2N,  or  Cy ;  eq.,  (12  -f. 
14=)  26. — This  is  a  gaseous  substance,-  and  is  readily  formed  by  heating 
bicyanide  of  mercury  (to  be  hereafter  described)  in  a  glass  retort  by  a 

QUESTIONS. — Will  it  answer  for  the  miner  to  remain  with  his  lamp  in 
the  explosive  mixture  ?  Describe  the  experiment  for  showing  the  opera- 
tion of  the  safety-lamp.  Will  wire  gauze  in  this  manner  prevent  the 
explosifn  of  mixtures  of  hydrogen  and  oxygen?  315.  What  is  said  of 
the  compounds  of  carbon  and  nitrogen  ?  From  what  does  cyanogen 
derive  its  name  ?  316.  How  is  bicarbonide  of  nitrogen,  or  cyanogen 
prepared  ? 


276       COMPOUND  OF  CARBON  AND  SULPHUR. 

epirit-lamp.  It  is  colorless,  has  a  very  pungent  odor,  and  is  easily  com- 
pressed into  a  liquid ;  and  by  the  cold  produced  by  a  mixture  of  solid 
carbonic  acid  and  sulphuric  ether,  this  liquid  may  be  frozen.  Of  the 
pure  gas,  100  cubic  inches  weigh  56-47  grains,  giving  it  a  density 
of  1-82. 

Cyanogen  is  composed  of  1  vol.  of  vapor  of  carbon  and  1  vol.  of 
nitrogen,  as  follows,  viz. : 

1  vol.  vapor  of  carbon  weighs  0-836 
-     1    «    nitrogen  "       0-972 


Weight  of  1  vol.  of -cyanogen,  1-80H 

Cyanogen,  though  a  compound,  is  remarkable  for  combining  with  the 
elementary  bodies  in  the  same  manner  as  an  element,  forming  a  class 
of  compounds  which  are  called  cyanides.  Further  remarks  concerning  it 
will  be  deferred  to  Organic  Chemistry. 


Compound  of  Carbon  and  Sulphur. 

317.  These  elements  combine  in  only  one  proportion,  forming 
the  following  compound : 

318.  Bisulphide  of  Carbon— CS2;  eq.,  (6  +  32  =)  38.— This 
compound,  called  also  sulplio-carbonic  acid,  is  formed  by  heating 
to  redness  pieces  of.  charcoal  in  a  porcelain  tube  or  retort,  and 
then  causing  vapor  of  sulphur  to  come  in  contact  with  it.     The 
figure  on  next  page  represents  a  good  arrangement  for  the  pur- 
pose, even  when  a  considerable  quantity  is  to  be  prepared.     The 
retort,  R,  of  stone  ware,  is  first  filled  with  pieces  of  well-burned 
charcoal,   and  the  tube  T  inserted   nearly  to  the  bottom,  and 
luted  well  around  the  neck,  to  prevent  any  escape  of  gaseous 
matter.     It  is  then  to  be  placed  in  a  suitable  furnace,  and  con- 
nected with  a  Liebig's  condenser,  C,  and  this  with  a  receiving 
vial,  V,  partly  filled  with  water.     A  small  tube  of  glass  inserted 
into  the  cork  allows  the  air  to  escape  as  the  vial  is  filled. 

QUESTIONS. — Describe  bicarbonide  of  nitrogen  or  cyanogen.  F6r  what 
is  it  remarkable?  317.  How  many  compounds  of  carbon  and  sulphur 
are  known?  318.  Describe  the  mode  of  preparing  bisulphide  of  carbon, 
or  sulpho-carbonic  acid. 


COMPOUND  01  CARBON  AND  SULPHUR. 


277 


Preparation  of  CSa. 


When  everything  is  ready,  a  fire  is  kindled  in  the  furnace,  and 
•when  the  retort  becomes  well  heated,  pieces  of  sulphur  are  occa- 
sionally dropped  into  the  tube  T,  and  a  cork  immediately  inserted. 
The  sulphur  being  sublimed  by  the  heat  comes  in  contact  with 
the  heated  charcoal,  with  which  it  combines,  producing  the  com- 
pound in  question.  This  now  passing  into  the  condenser,  takes 
the  liquid  form,  and  is  collected  in  the  receiver,  V. 

It  will  be  observed  that  this  process  is  a  case  of  combustion 
(193),  the  carbon  being  the  combustible,  and  the  vapor  of  sul- 
phur the  supporter ;  and  the  compound  formed,  CS2,  is  analogous 
to  carbonic  acid,  C02,  which  is  formed  when  carbon  is  burned  in 
oxygen.  And  as  carbonic  acid  combines  with  oxy bases,  to  form 
salts,  the  composition  of  which  is  RO,C02,  so  sulphide  of  carbon 
combines  with  sulphur  bases,  to  form  compounds  of  the  analogous 
form,  RS,CS2.  The  letter  B  is  here  used  indefinitely,  for  any 
element  whatever. 

Bisulphide  of  carbon  is  a  colorless  liquid,  which  boils  at  about 
112°,  and  has  a  density  of  1-27.  It  does  not  mix  with  water, 
but  dissolves  readily  in  alcohol  or  ether.  Its  odor  is  excessively 
fetid  and  nauseous.  Both  sulphur  and  phosphorus  are  dis- 
solved in  it,  and  may  be  obtained  in  crystals  by  the  gradual 

QUESTIONS. — What  is  said  of  the  relation  of  bisulphide  of  carbon  to 

carbonic  acid  ?     May  this  be  considered  as  a  case  of  combustion  ?    Which 

of  the  substances  is  to  be  considered  as  the  combustible  body,  and  which 

the  supporter  ?    What  are  some  of  the  properties  of  bisulphide  of  carbon  ? 

24 


278  SILICON. 

evaporation  of  the  solution.  By  its  evaporation  iu  the  open  air  a 
very  considerable  cold  is  produced,  but  under  the  receiver  of  the 
air-pump  its  evaporation  is  so  rapid  as  to  occasion  a  cold  of — 76°. 
It  burns  freely  in  the  open  air,  producing  carbonic  and  sulphurous 
acids,  and  with,  oxygen  its  vapor  forms  an  explosive  mixture. 


SILICON. 

Symbol,  Si;  Equivalent,  21-3;  Density,  ?. 

319.  History. — Silicon  was  first  obtained  by  Berzelius,  in  1824. 
It  was  then  considered  a  metal,  and  named  silicium,  but  is  now 
generally  ranked  with  the  non-metallic  elements.      It  is  never 
found  in  its  separate  state  in  nature,  although  it  is  really  very 
abundant  in  every  place  in  silicic  acid  (silica),  and  the  various 
siliceous  compounds  which  constitute  the  rocks  and  soils.     Next 
to  oxygen  it  is  the  most  abundant  element  found  upon  the  earth. 

320.  Preparation. — To  prepare  silicon  a,  somewhat  complex 

substance  is  selected,  the  double  fluoride 
of  silicon  and  potassium,  which  is  a  white 
powder  like  starch. 

When  this  compound  is  heated  in  a 
glass  tube  with  nearly  its  own  weight 
of  potassium,  by  means  of  a  spirit-lamp, 
the  fluorine  combines  with  the  potassium, 
and  the  silicon  is  separated  from  the  mass 
by  washing  with  water,  which  dissolves 

the  fluoride  of  potassium  and  leaves  the  silicon  very  pure. 

The  reactions  which  take  place  are  represented  by  the  following 

equation : 

3KF,2SiF3  +  6K  =  9KF  +  2Si. 


QUESTIONS. — 319.  Has  silicon  sometimes  been  ranked  with  the  metals  ? 
Is  it  abundant  in  nature  ?     320.  How  may  it  be  prepared  ? 


COMPOUND    OP    SILICON   AND   OXYGEN.  279 

321,  Properties. — Silicon,  as  thus  obtained,  is  a  powder  of  a 
dark,  nut-brown  color,  without  metallic  lustre,  and  is  a  non-con- 
ductor of  heat  and  electricity.  It  stains  the  fingers,  and  adheres 
to  everything  that  comes  in  contact  with  it ;  and  when  heated  in 
the  atmosphere  or  oxygen  gas,  it  takes  fire  and  burns,  with  the 
formation  of  silicic  acid. 

In  close  vessels,  silicon,  like  charcoal  and  boron,  is  capable 
of  enduring  a  very  high  temperature  without  fusion,  but  is  ren- 
dered harder  and  more  compact.  It  is  now  incombustible,  even 
when  highly  heated  in  the  air  or  in  oxygen  gas,  and  is  unaffected 
by  the  blowpipe,  even  in  contact  with  chlorate  of  potassa. 


Compound  of  Silicon  and  Oxygen. 

322,  There  is  known  only  a  single  compound  of  these  elements, 
the  teroxide,  Si03. 

323.  Silicic  Acid,  or  Silica— Si03;  eq.,  (21-3  +  24=)  45-3. 
— This  is  one  of  the  most  abundant  compounds  in  nature,  and  is 
found  quite  pure  in  quartz,  flint,  calcedony,  agate,  &c. ;  and,  in 
combination  with  qther  substances,  in  the  material  of  all  soils,  and 
nearly  all  rocks. 

Alone,  silica  is  nearly  infusible,  but  may  be  melted  in  the 
intense  heat  of  a  compound  blow-pipe.  It  is  not  acted  upon  by 
any  acid  except  the  hydrofluoric  (252),  but,  at  high  temperatures, 
enters  into  combination  with  the  alkalies  and  earths.  It  is  very 
hard,  and  has  a  harsh  feeling  to  the  fingers,  even  in  fine  powder. 
In  quartz  crystals,  which  are  usually  six-sided  prisms,  terminated 
by  six-sided  pyramids,  it  is  familiar  to  every  one. 

By  heating  silica  in  fine  powder,  with  four  times  its  weight 
of  carbonate  of  potash}  in  a  platinum  crucible,  the  carbonic  acid 
is  displaced,  and  silicate  of  potash  formed;  which,  being  treated 

QUESTIONS. — 321.  Describe  the  properties  of  silicon.  322.  What  com- 
pound only  of  silicon  and  oxygen  is  there?  323.  What  is  said  of  the 
abundance  of  silicic  acid,  or  silica  ?  What  is  said  of  its  fusibility  ?  Is  it 
acted  upon  by  any  of  the  acids  ?  What  is  the  usual  form  of  its  crystals  ? 
What  is  the  eifect  when  silica  in  fine  powder  is  heated  with  carbonate 
of  potash  ? 


2 30  OTHER   COMPOUNDS   OF   SILICON. 

with  diluted  hydrochloric  acid,  yields  a  gelatinous  precipitate  of 
hydrated  silica.  This  is  soluble  in  water,  and  constitutes  soluble 
glass,  or  liquor  of  flints, — terms  sometimes  used.  It  is  some- 
times found  in  the  waters  of  hot  springs,  as  the  Geysers  of  Ice- 
land; and,  in  fact,  in  very  small  quantities,  in  most  natural 
waters.  In  this  state  it  is  taken  up  by  the  rootlets  of  plants,  and 
is  found  in  their  ashes  after  incineration.  It  is  especially  abun- 
dant in  the  grasses  and  the  straw  of  the  cereal  grains,  and  in  the 
stalks  of  rushes  and  reeds. 

In  the  gelatinous  state,  silica  has  occasionally  been  found  in 
the  cavities  of  minerals,  when  they  have  been  broken.  Exposed 
to  the  air,  and  especially  if  heated,  the  water  evaporates,  and  dry, 
tfarsh,  insoluble  silica  only  remains. 

All  the  different  varieties  of  glass  are  silicates  of  different 
bases,  or  mixtures  of  these  silicates.  This  subject  will  be  treated 
of  more  at  length  hereafter. 

It  is  in  its  power  thus  to  combine  with  the  bases,  so  as  perfectly  to 
neutralise  them,  that  this  compound,  oxide  of  silicon,  or  silica,  evinces 
its  Claims  to  be  considered  as  an  acid. 


Other  Compounds  of  Silicon. 

324.  Terchloride  of  Silicon— SiCl? ;  eq.,  (21-3  -f  106-2  ==)  127-5.— This 
compound  is  formed  by  heating  silicon  in  dry  chlorine,  or  by  passing  a 
current  of  the  latter  over  a  mixture  of  silica  and  carbon  when  heated  in 
a  porcelain  tube.     It  is  a  colorless,  volatile  liquid,  which  boils  at  about 
138°,  and  has  a  density  of  about  1-52.     By  contact  with  water  it  is  de- 
composed, producing  silica  and  hydrochloric  acid. 

325.  Terfluoride   of  Silicon  —  SiF? ;    eq.,  (21  <3  -f  57  =)  78-3.  —  This 
fluoride,  called  also,  fluo- silicic  acid,  is  obtained  by  gently  heating  a  mix- 
ture of  equal  parts  of  dry  and  finely-powdered  glass  and  fluor-spar,  made 
into  a  paste  with  strong  oil  of  vitriol.     The  oxygen  of  the  silica  and  the 
fluorine  of  the  fluor-spar  here  exchange  places,  while  the  sulphuric  acid 
combines  with  the  lime  that  is  formed,  thus,  neglecting  the  water  of 
the  sulphuric  acid, 

3CaF  -f  Si03  -f  3S03  =  3(CaO,S03)  -f-  SiF3. 

QUESTIONS. — Is  silica  found  in  nature  ?  Is  it  taken  up  by  the  roots 
of  plants  ?  Of  what  are  all  the  different  kinds  of  glass  composed  ? 
824.  How  is  the  terchloride  of  silicon  formed  ?  Describe  its  properties. 
826.  Describe  the  terfluoride  of  silicon. 


BORON.  281 

Terfluoride  of  silicon  is  a  colorless  gas,  with  a  pungent,  acid  odor,  and 
in  the  open  air  forms  dense  white  fumes  by  combining  with  the  moisture 
it  contains.  Its  density  is  3-57. 

By  contact  with  water  it  is  at  once  decomposed,*  gelatinous  silAca  is 
deposited,  and  the.  water  is  found  to  contain  a  peculiar  compound,  called 
hydrofluo silicic  acid,  the  composition  of  which  is  3HF,  2SiF3. 

The  experiment  is  best  performed  by  putting  the  materials  in  »  dry 
retort,  A,  connected  with  a  receiver,  R,  partly  filled  with  wata  c^itd 


placed  so  that  it  can  be  gently  shaken  occasionally,  in  order  that  the 
film  of  silica  forming  upon  the  surface  may  be  broken  up,  and  a  fresh 
surface  of  water  exposed. 

When  hydrofluosilicic  acid  is  saturated  with  a  base,  as  potassa,  the 
hydrogen  is  replaced  by  an  equivalent  quantity  of  the  metal  of  the  base. 
Thus, 

3HF,,2SiF3  4-  3KO  =  3KF,2SiF3  -f  3HO. 

The  compound  3KF,2SiF3  is  the  double  fluoride  of  silicon  and  potas- 
sium (320)  used  in  the  preparation  of  silicon. 

Silicon  is  capable  also  of  forming  compounds  with  sulphur  and  bromine. 


BORON. 
Symbol j  B;  Equivalent,  10-9;  Density,  2. 

326.  History. — Boron,  in  a  separate  state,  was  first  obtained 
by  Davy,  in  1807.  It  is  found  in  nature  only  in  combination, 
and  in  comparatively  small  quantities.  Though  it  occurs  in 

QUESTIONS. — How  is  terfluoride  of  silicon  affected  by  contact  with 
water?  What  is  the  composition  of  hydrofluosilic  acid?  326.  When 
and  by  whom  was  boron  discovered  ?  Is  it  found  naturallv  in  a  separate 
state? 

24* 


282  BORON. 

several  minerals,  as  datholite  and  boracite,  it  is  obtained  chiefly 
from  the  waters  of  certain  hot  springs,  especially  in  Tuscany  and 
the  Lipari  Islands,  where  it  occurs  in  solution,  as  boracic  acid. 

327.  Preparation. — To  prepare  boron,  first  make  a  saturated 
solution  of  borax  in  boiling  water,  and,  while  hot,  pour  in  sul- 
phuric or  hydrochloric   acid  until   the   solution  tastes  distinctly 
sour.     As  it  cools  the  boracic  acid  will  separate  in  white,  shining 

scales,  which  are  to  be  thoroughly  washed 
and  dried  by  fusion  in  a  platinum  cru- 
cible. We  thus  obtain  boracic  acid,  which 
is  then  to  be  mixed  with  potassium  (or 
sodium),  and  heated  in  a  glass  tube,  as 
in  the  preparation  of  silicon.  A  part  of 
the  boracic  acid  yields  its  oxygen  to  the 
potassium,  and  the  potassa  so  formed  enters 
into  combination  with  the  rest  of  the 
boracic  acid  to  form  borate  of  potassa.  By  treating  the  mass 
with  cold  water  the  latter  compound  is  dissolved,  and  the  boron 
is  seen  floating  in  the  liquid  as  a  fine  powder  of  a  brownish  color, 
and  may  be  collected  on  a  filter.  Before  filtering,  some  sal  am- 
monia should  be  dissolved  in  the  mixture,  which  has  the  effect 
to  prevent  the  escape  of  the  finely-powdered  boron  through 
the  filter. 

The  mode  in  which  the  sal  ammonia  operates  to  produce  this 
effect  is  not  understood. 

328,  Properties. — Boron  is  a  dark  olive-green  powder,  without 
taste  or  smell,  and  incapable  of  fusion  in  the  strongest  heat.     It 
is  insoluble  in  water  or  alcohol.     Heated  in  the  open  air  to  about 
600°,  it  takes  fire  and  burns  brilliantly,  forming  boracic  acid.     It 
is  a  non-conductor  of  electricity  and  heat. 

* 

QUESTIONS. — 327.    How  is  boron  prepared?  -Describe  the  reactions 
which  occur.     328.  Describe  boron.     How  is  it  affected  whjen  heated  ? 


OTHER  COMPOUNDS   OP  BORON.  283 


Compound  of  Boron  and  Oxygen. 

329.  Boracic  Acid— B£<(;  eq.,  (10-9  +24=)  34-9.— This 
acid  may  be  obtained  from  the  common  borax  of  commerce, 
as  just  described  in  the  preparation  of  boron ;  it  is  also  produced 
by  the  combustion  of  boron  in  the  air. 

Boracic  acid  is  slightly  soluble  in  water  and  in  alcohol ;  and 
when  the  latter  solution  is  inflamed  it  communicates  to  the  flame 
a  beautiful  green  tinge, 
which  is  characteristic 
of  this  substance.  To 
make  the  experiment, 
fill  a  common  dropping 
tube,  of  the  form  A  B 
in  the  figure,  with  the 
solution  ;  and,  inserting  Green  Flame  produced  by  B°8' 

a  cork  firmly  in  A,  apply  the  heat  of  a  lamp  to  the  bulb,  and 
inflame  the  jet  of  liquid  as  it  issues  from  the  capillary  orifice,  B. 
The  flame  will  be  of  a  beautiful  green. 

The  color  of  the  flame  may  also  be  shown  very  well  simply 
by  moistening  one  end  of  a  pine  stick  in  the  solution,  and  in- 
flaming it. 

Other  Compounds  of  Boron. 

.330.  Terchloride  of  Boron— BC13;  eq.,  (10-9  +  106-2=)  117-1.— This 

compound  is»  formed  by  preparing  an  intimate  mixture  of  boracic  acid 
and  carbon,  and  causing  a  current  of  dry  chlorine  to  pass  over  it  in  a 
porcelain  tube,  kept  at  a  red  heat.  It  is  a  colorless  gas,  of  a  density  of 
4-03 ; — iu  the  open  air  it  forms  dense  white  fumes  with  the  moisture  con- 
tained therein,  and  in  contact  with  liquid  water  it  is  instantly  decom- 
posed, forming  hydrochloric  and  boracic  acids. 

331.  Terfluoride  of  Boron— BF3;  eq.,  (10-9  -f  57  =)  67-9.— Terfluoride 
of  buron,.or  fluoboracic  acid,  is  a  colorless  gas,  of  specific  gravity  2-37. 
It  is  prepared  by  heating  in  a  gun-barrel  a  mixture  of  2  parts  of  pul- 

QFESTIONS. — 329.  How  is  boracic  acid  procured  from  borax  ?  Describe 
this  acid.  What  color  does  it  give  to  the  flame  of  alcohol  when  dissolved 
in  it  ?  How  may  it  be  shown  ?  330.  How  is  the  terchloride  of  boron 
formed?  331.  How  is  the  terfluoride  of  boron  formed? 


284        THE  METALS. —  GENERAL  PROPERTIES. 

verized  fluor  spar  (fluoride  of  calcium),  and  1  part  of  fused  boracic  acid. 
It  has  a  strong  affinity  for  water,  which  dissolves  700  or  800  times  its 
own  volume  of  the  gas,  and  acquires  a  sour  taste  and  a  strong  acid 
reaction,  and  chars  wood  like  oil  of  vitriol  when  brought  in  contact  with  it. 
Boron  combines  also  with  sulphur,  forming  a  tersulphide,  BS8. 


THE  METALS. 
General  Properties. 

332.  Characteristic  Properties,  —  The  metals  are  generally 
good  conductors  of  electricity  and  heat,  and  possess  a  peculiar 
lustre  called  the  metallic  lustre,  which  can  scarcely  be  imitated  by 
other  substances.      When  their  compounds  are  decomposed  by 
the  galvanic  battery,  they  always  make  their  appearance  at  the 
negative  electrode  (112),  and  are  therefore,  without  exception,  to 
be  considered  as  electro-positive.     But  these  properties  are  much 
more  distinct  in  some  metals  than  in  others.     Most  of  the  metals 
are  also  characterized  by  their  great  density,  as  gold  and  platinum  ; 
but  two  at  least,  potassium  and  sodium,  are  lighter  than  water. 
All  of  them  except  mercury  are  solid  at  ordinary  temperatures. 

The  ancients  were  acquainted  with  only  seven  metals,  viz. : 
gold,  silver,  iron,  copper,  mercury,  lead,  and  tin ;  but  there  are 
now  known,  with  certainty,  forty-seven;  and  the  discovery  of 
several  others  has  been  announced,  though  perhaps  not  fully 
proved. 

333,  Sources  of  the  Metals. — Though  several  o£  the  metals 
are  found  in  animal  and  vegetable  substances,  they  seem  to  form 
no  necessary  part  of  any  organic  compounds.     Most  of  them,  as 
iron   lead,  and  zinc,  are  found  in  the  earth  in  combination  with 
other  non-metallic  elements,  as  oxygen,  sulphur,  or  arsenic,  and 
are  said  to  be  mineralized,  and  the  compound  is  called  an  ore  ; 
but  a  few,  as  platinum,  gold,  and  sometimes  copper,  silver,  bis- 

QUESTIONS.— 332.  What  are  some  of  the  characteristic  properties  of  the 
metals  ?  How  many  metals  were  known  to  the  ancients  ?  Are  all  the 
metals  solid  at  ordinary  temperatures  ?  333.  Do  any  of  the  metals  form 
any  part  of  organic  compounds  ?  What  constitutes  a  metallic  ore  ? 


THE   METALS.  —  GENERAL   PROPERTIES.  285 

muth,  &c.,  occur  in  the  metallic  state,  and  are  said  to  be  found 
native.  Some  are  found  in  the  form  of  salts,  especially  as  sili- 
cates, carbonates,  and  sulphates. 

The  metals  occur  sometimes  in  &er/s,  which  are  more  or  less 
parallel  with  the  earthy  strata  containing  them,  but  more  fre- 
quently in  veins  or  lodes,  which  traverse  the  strata  in  every 
direction.  The  veins  are  more  abundant  in  the  older  than  in  the 
newer  rocks ;  and  their  appearance  indicates  that  they  are  fissures 
which  have  been  produced  in  the  strata  subsequent  to  their 
deposition,  and  then  filled  by  filtration  of  the  metallic  matter 
from  above,  or  by  injections  from  below.  Besides  the  metallic 
compounds,  or  ores,  these  veins  always  contain  other  minerals,  as 
quartz,  carbonate  of  lime,  heavy  spar,  and  fluor  spar,  which  con- 
stitute the  gangue,  or  vein-stone. 

334.  Relations  to  Li^ht, — The  relations  of  the  metals  to  light 
are  in  some  respects   peculiar  and  interesting.      Their  peculiar 
lustre,   called  the  metallic  lustre,  has  already  been  alluded  toj 
this  lustre  entirely  disappears  when  they  are  reduced  to  a  fine 
powder,   but   reappears  when    the   substance  is  rubbed  with  a 
burnisher. 

All  the  metals  except  gold  are  perfectly  opake,  even  when  reduced  to 
the  thinnest  laminae  possible.  Gold  in  the  form  of  leaf  transmits  a  feeble 
green  light.  The  best  method  to  observe  this  light  is  to  place  an  un- 
broken leaf  upon  a  piece  of  white  plate  glass,  and  press  it  gently  with  a 
bunch  of  cotton  to  make'  it  adhere.  It  may  then  be  preserved  for  any 
length  of  time. 

The  color  of  most  of  the  metals,  seen  in  mass,  is  grayish-white, 
as  platinum,  iron,  lead,  and  potassium,  but  seen  in  powder  the 
color  is  a  deep  gray.  By  burnishing  the  particles,  the  original 
grayish-white  is  restored.  Gold  in  mass  has  a  beautiful  yellow 
color,  and  in  powder  a  deep  purple,  almost  black.  Copper  and 
titanium  i*re  red. 

335.  Malleability  and  Ductility. — Some  metals  possess  the 
property  of  malleability,  that  is,  admit  of  being  beaten  into  thin 

QUESTIONS. — When  is  a  metal  said  to  be  found  native?  334.  What  is 
said  of  the  lustre  of  the  metals  ?  Is  this  lustre  seen  in  a  metal  when  it  is 
reduced  to  .powder  ?  Are  most  of  the  metals  opake  even  when  reduced 
to  thin  laminae  ?  What  is  the  color  of  most  of  the  metals  ?  What  ia 
said  of  their  color  when  in  fine  powder?  What  metal  is  yellow?  What 
.  metals  are  red  ?  335.  What  malleable  metals  are  mentioned  ? 


286  THE   METALS. —  GENERAL   PROPERTIES. 

plates  or  leaves  by  hammering.  The  malleable  metals  are  gold, 
silver,  copper,  tin,  platinum,  palladium,  cadmium,  lead,  zinc,  iron, 
'nickel,  potassium,  sodium,  aluminum,  and  frozen  mercury.  The 
other  metals  are  either  malleable  in  a  very  small  degree  only,  or, 
like  antimony  and  bismuth,  are  actually  brittle.  Gold  surpasses 
all  the  other  metals  in  malleability ;  one  grain  of  it  may  be 
extended  so  as  to  cover  about  52  square  inches  of  surface,  and 
the  film  will  have  a  thickness  of  only  ^-^o^th  of  an  inch. 

Nearly  all  malleable  metals  may  be  drawn  out  into  wires,  a 
property  which  is  expressed  by  the  term  ductility.  The  only 
metals  which  are  remarkable  in  this  respect  are  gold,  silver, 
platinum,  iron  and  copper. 

The  process  of  wire-drawing  consists  in  drawing  the  metal 
through  round  holes  macfe  in  plates  of  steel  for  the  purpose.  The 
steel  plate  is  made  with  a  number  of  holes,  of  different  diameters, 
through  which  the  rod  of  metal  is  made  to  pass  successively,  its 
diameter  at  each  operation  being  a  little  reduced  andvits  length 
increased. 

A  machine  for  this  purpose  is  represented  by  the  accompanying  figure. 
AB  is  the -plate  of  steel  through  which  the  wire  is  drawn, — it  is  held 


Wire  Drawing. 


firmly  in  its  place  by  a  support,  D.     A  rod  from  the  rolling  mill,  in  tLo 
form  of  a  coil,  or  a  coil  of  wire,  is  placed  upon  the  reel,  F  G,  which  turns 

QUESTIONS. — What  metals  are  mentioned  as  being  brittle  ?  What  is 
said  of  the  malleability  of  gold  ?  Are  the  malleable  metals  also  ductile  ? 
Describe  the  process  of  wire-drawing  ? 


THE   METALS.— GENERAL   PROPERTIES.  287 

easily  upon  its  axis ;  and  the  end  of  the  wire,  drawn  out  a  little  with  the 
h;umnr-r,  is  passed  through  the  plate  and  attached  to  the  drum,  C,  which 
is  turned  by  machinery,  and  by  its  motion  winds  the  wire  around  itself, 
at  the  same  time,  of  course,  withdrawing  it  from  the  reel.  To  form 
small  wire  it  is  in  this  way  passed  many  times  through  the  plate ;  and, 
to  prevent  its  becoming  hard  and  brittle,  it  is  several  times  annealed 
during  the  process.  The  passage  of  the  wire  through  the  plate  is  facili- 
tated by  dipping  the  coils  occasionally  in  a  moderately  strong  solution 
of  sulphate  of  copper,  by  which  it  receives  a  thin  coating  of  metallic 
copper. 

336.  The  malleability  and  ductility  of  any  substance  would 
seem  to  depend  very  nearly  upon  the  same  properties,  but.  i*  is 
found  in  the  case  of  metals  that  they  are  not  precisely  the  same. 
In  the  following  table,  in  the  first  column,  several  of  the  metals 
are  arranged  in  the  order  of  their  malleability,  beginning  with 
the  most  malleable  j  in  the  second  column,  the  same  metals  are 
arranged  in  the  order  of  their  ductility.  The  table  is  from 
Regnault. 


Malleability. 

1.  Gold. 

2.  Silver. 

3.  Copper. 

4.  Tin. 

5.  Platinum. 

6.  Lead. 

7.  Zinc. 

8.  Iron. 

9.  Nickel. 


Ductility. 

1.  Gold. 

2.  Silver. 

3.  Platinum. 

4.  Iron. 

5.  Nickel. 

6.  Copper. 

7.  Zinc. 

8.  Tin. 

9.  Lead. 


Both  the  malleability  and  ductility  of  several  of  the  metals 
vary  with  the  temperature.  Thus  iron,  though  partially  malle- 
able and  ductile  at  the  ordinary  temperature  of  the  atmosphere, 
is  much  more  so  at  a  red  heat ;  and  zinc  is  very  malleable  from 
212°  to  350°,  but  loses  this  property  if  cooled  down  to  32°,  or 
heated  to  600°.  At  the  latter  temperature  it  is  decidedly  brittle. 

When  ,a,  metal  has  been  hammered  or  rolled,  or  drawn  out  into 
wire,  its  hardness  as  well  as  density  is  increased ;  and  it  becomes 
less  malleable.  This  property,  however,  is  restored  by  annealing 
it,  which  consists  in  heating  it  to  redness  and  then  cooling  it 

QUESTIONS. — 336.  Do  the  malleability  and  ductility  of  a  substance 
depend  upon  the  same  properties  ?  Are  the  malleability  and  ductility 
of  some  of  the  metals  affected  by  their  temperature?  What  is  said 
of  iron  and  zinc  in  this  connection  ?  What  is  meant  by  the  annealing 
of  a  metal  ?  Why  is  this  often  necessary  in  working  many  of  the  metals  ? 


288 


THE    METALS. GENERAL   PROPERTIES. 


slowly.     But  the  tenacity  is  often  very  much  diminished  by  the 
process,  sometimes  even  more  than  one-half. 

337.  The  tenacity  of  a  metal  is  determined  by  ascertaining  the 
greatest  weight  a  wire  made  of  it,  of  a  given  diameter,  will   sus- 
tain.    The  determination  is  made  by  attaching   one  end  of  the 
wire  to  a  firm  support,  and  to  the  other  end  fixing  a  pan  to 
receive  the  weights.     Wires  0-787  of  a  line  in  diameter  (=  to 
about  TJftth  of  an  inch),  made  of  the  several  metals  mentioned 
below,  were  loaded  gradually  until  they  broke  with  the  weights 
placed  opposite  to   tfceir  names  in  the  following  table.      These 
numbers  therefore  indicate  their  relative  tenacities. 

Pounds. 

Iron  wire  549  Gold 

Copper .V  302  Zinc 

Platinum 274  Tin 

Silver 187  Lead 27 

When  a  metallic  wire  is  tested  in .  this  manner  its  length  is 
increased  with  the  weight,  but  if  the  load  has  not  been  too  great 
it  contracts  again  to  the  same  length  as  at  first,  on  the  removal 
of  the  load.  If  the  load  be  increased  beyond  a  certain  point,  a 
permanent  elongation  is  produced ;  and  usually  no  great  further 
increase  is  needed  to  break  the  wire. 

338.  The  specific  gravity  of  the  metals,  like  many  of  their 
other  properties,   are  very  dissimilar.     The  specific  gravities  of 
some  of  the  more  important  of  them  are  contained  in  the  following 


Table  of  the  Specific  Gravity  of  Metals 

Platinum 20-98  • 

Gold 19-02 

Tungsten 17-65 

Mercury 13-56 

Palladium 11-05 

Lead 11-35 

Silver 10-47 

Bismuth 9-82 

Uranium 9-00 

Copper 8-09 

Cadmium 8-60 

Molybdenum 8-00 


at  60°,  compared  with  Water  as  Unity. 

Cobalt 8-53 

Nickel 8-27 

Manganese 8-01 

Iron 7-78 

Tin 7-29 

Zinc 6-86 

Antimony 6-70 

Chromium 5-09 

Titanium 5-03 

Aluminum 3-07 

Sodium 0-97 

Potassium ,..     ..  0-86 


QUESTIONS. — 33l  How  is  the  tenacity  of  a  metal  determined?  What 
metal  of  those  mentioned  has  the  greatest  tenacity  ?  What  is  the  second  ? 
338.  What  is  said  of  the  specific  gravity  of  the  metals  ?  What  metal  is 
mentioned  as  having  the  greatest  specific  gravity  ?  What  is  the  second  ? 


THE    METALS. —  GENERAL    PROPERTIES.  289 

it 

339.  Crystaline  Characters. — Many  of  the  metals  have  a  dis- 
tinctly cry  stall  ne   texture.      Iron,  for  example,  is  fibrous;   and 
zi*»c,  bismuth,  and  antimony  aro  lamellated.     Metals  are  some- 
times obtained  also  in  crystals — and  most  of  them,  in  crystalizing, 
assume  the  figure  of  the  cube,  the  regular  octahedron,  or  some 
form  allied  to  it.     Gold,  silver,   and  copper  occur  naturally  in 
crystals,  while  others  crystalize  when  they  pass  gradually  from 
the  liquid  to  the  solid  condition.     Crystals  are  most  readily  pro- 
cured from  those  metals  which  fuse  at  a  low  temperature ;  and 
bismuth,  from  conducting  heat  less  perfectly  than  other  metals, 
and,  therefore,  cooling  more  slowly,  is  best  fitted  for  the  purpose. 

Several  of  the  metals  form  small  but  very  beautiful  crystals,  as 
they  are  slowly  separated  from  their  solutions  by  the  galvanic 
current.  If  in  a  solution  of  sulphate  of  copper  we  place  two 
plates  of  copper,  and  connect  them  with  the  two  electrodes  of  a 
galvanic  battery  in  feeble  action,  after  some  time  the  plate  on  the 
negative  side  will  become  covered  with  small  crystals  of  metallic 
copper,  while  the  other  plate  will  be  gradually  dissolved. 

It  is  believed  that  some  of  the  metals,  in  certain  peculiar  circum- 
stances, may  assume  a  crystalline  structure,  even  when  in  the  solid 
state. 

340.  Alloys. — Many  of  the  metals  are  capable  of  combining 
with  each«other,  forming  compounds  called  alloys,  which  will  be 
described  in  their  proper  places.     They  possess  all  the  charac- 
teristic physical  properties  of  the  pure  metals,  and  many  of  them 
are  of  great  service  in  the   arts.      Generally,  alloys  are  more 
fusible  and   more   oxidable   than  their  constituents   separately. 
Their  malleability  and  ductility  usually  are  much  less,  and  their 
hardness  greater,  than  those  of  the  metals  of  which  they  are 
composed. 

Compounds  of  mercury  with  other  metals  are  called  amalgams. 

341.  Metallurgy.— The  reduction  of  the  metals  from  their 
ores,  and  the  methods  adopted  in  working  them  in  the  arts,  con- 

QUESTIO-NS. — 339.  Do  any  of  the  metals  possess  a  crystaline  texture  ? 
What  metals  are  mentioned  as  being  sometimes  found  in  crystals  ?  De- 
scribe the  mode  of  obtaining  crystals  of  copper  by  the  galvanic  process  ? 
840.  What  are  alloys  ?  Do  alloys  possess  the  usual  physical  propertiea 
of  the  metals  ?  What  is  said  of  their  fusibility  ?  What  of  their  malle- 
ability and  ductility  ?  What  are  amalgams  ?  341.  What  is  metallurgy  ? 
25 


290  THE   METALS. —  GENERAL  PROPERTIES. 

* 

stitutea  a  distinct  branch  of  chemical  science,  called  by  this 
name.  Most  of  the  metals  have  an  extensive  range  of  affinity; 
many  of  them  form  compounds  with  nearly  all  the  non-metallic 
elements,  and  all  without  exception  combine  with  oxygen. 

As  many  of  the  metallic  ores  are  oxides,  the  reduction  of  this 
class  of  compounds  becomes  particularly  important.  It  is  effected 
in  several  different  modes,  as, 

1.  By  mere  heat.     By  this  method  the  oxides  of  gold,  silver, 
mercury,  and  platinum  may  be  decomposed. 

2.  By  the  united  agency  of  heat   and   combustible  matter. 
Thus,  by  transmitting  a  current  of  hydrogen  gas  over  the  oxides 
of  copper  or  iron  heated  to  redness  in  a  tube  of  porcelain,  water 
is  generated,  and  the  metals  are  obtained  in  a  pure  form.     Car- 
bonaceous matters  are  likewise  used  for  the  purpose  with  great 
success.     Potassa  and  soda,  for  example,  may  be  decomposed  by 
exposing  them  to  a  white  heat,  after  being  intimately  mixed  with 
charcoal    in   fine   powder.      A  similar  process  is   employed    in 
metallurgy  for  extracting  metals  from  their  ores,  the  inflammable 
materials  being  wood,  charcoal,  coke,  or  coal.     In  the  more  deli- 
cate operations  of  the  laboratory,  charcoal  and  Hack  flux*  are 
employed. 

3.  By  the  galvanic  battery.     This  is  a  still  more  powerful 
agent  than  the  preceding;   since  some  oxides,  such  as  baryta 
and  strontia,  which  resist  the  united  influences  of  heat  and  char- 
coal, are  reduced  by  the  agency  of  galvanism. 

4.  By  the  action  of  deoxdizing  agents  on  metallic  solutions. 
Phosphorous  acid,  for  example,  when  added  to  a  liquid  containing 

'  oxide  of  mercury,  deprives  the  oxide  of  its  oxygen,  metallic  mer- 
cury subsides,  and  phosphoric  acid  is  generated.  In  like  manner 
one  metal  may  be  precipitated  by  another,  provided  the  affinity 
of  the  latter  for  oxygen  exceeds  that  of  the  former.  Thus,  when 
mercury  is  added  to  a  solution  of  nitrate  of  oxide  of  silver, 
metallic  silver  is  thrown  down,  and  oxide  of  mercury  is  dissolved 

> 

*  Black  flux  is  prepared  by  deflagrating  nitre  with  twice  its  weight  of  cream  of  tartar 
When  equal  weights  are  used,  it  constitutes  white  Jlux. 

QUESTIONS. — What  is  said  of  the  affinity  of  the  metals?  What  are 
most  of  the  metallic  ores?  What  are  some  of  the  different  means  by 
which  these  ores  may  be  reduced  ? 


SALINE   COMPOUNDS,    OR   SALTS.  291 

by  the  nitric  acid.  On  placing  metallic  copper  in  the  liquid,  pure 
mercury  subsides,  and  a  nitrate  of  the  oxide  of  copper  is  formed; 
and  from  this  solution  metallic  copper  may  be  precipitated  by 
means  of  iron. 

To  reduce  the  other  compounds  of  the  metals,  other  modes  are  adopted, 
which  cannot  here  be  particularly  described. 

The  relations  of  the  various  metalloids  to  the  metals  will  be  described 
as  each  of  these  latter  elements  shall  come  in  review  before  us,  so  far  as 
demanded  by  the  special  object  of  the  work. 

342.  Classification  of  the  Metals,  —  The  metals  have  been 
variously  classified  by  different  writers ;  but  the  following  arrange- 
ment into  six  groups  will  probably  answer  our  purpose  as  well  as 
any  we  can  adopt. 

1.  Metals,  the  protoxides  of  which  are  alkalies. 

2.  Metals,  the  protoxides  of  which  are  alkaline  earths. 

3.  Metals,  the  protoxides  or  sesquioxides  of  which  are  earths. 

4.  Metals  which,  at  a  red  heat,  decompose  the  vapor  of  water, 
but  are  not  actecl  upon  by  liquid  water. 

5.  Metals  which  are  incapable  of  decomposing  water,  and  whose 
oxides  are  not  reduced  by  the  mere  action  of  heat. 

6.  Metals  whose  oxides  are  reduced  by  a  red  heat. 


Saline  Compounds,  or  Salts. 

343,  A  salt  is  a  compound  of  two  other  binary  compounds, 
which  sustain  to  each  other  the  relation  of  acid  and  base ;  the 
former  being  electro-negative  in  reference  to  the  latter,  which 
is  electro-positive.  Thus,  sulphate  of  soda,  NaO,S03,  is  a  com- 
pound of  sulphuric  acid  (teroxide  of  sulphur)  and  soda,  which  is 
the  protoxide  of  sodium;  the  former  being  electro-negative  in 
reference  to  the  latter,  which  is  electro-positive. 

The  acids  take  their  name  from  the  fact  that  when  soluble 
their  taste  is  very  gen-erally  sour, — but  this  may  not  always  be 

QUESTIONS. — 342.  What  are  the  metals  included  in  the  first  group? 
In  the  second  group  ?  In  the  third  ?  In  the  fourth  ?  In  the  fifth  ?  In 
the  sixth?  343.  What  is  a  salt?  Illustrate  by  an  example.  How  are 
the  acids  generally  characterized  ? 


292  SALINE    COMPOUNDS,    OR    SALTS. 

the  case;  they  are  mostly  combinations  of  two  metalloids,  as  the 
sulphuric,  nitric,  and  hydrochloric  acids,  but  sometimes  they  are 
formed  of  a  metal  and  metalloid,  as  the  manganic  and  chromic- 
acids,  and  the  sulphides  of  tin  and  antimony,  which  are  capable 
of  acting  as  acids.  Most  of  them  have  the  property  of  changing 
the  blue  solution  of  litmus  to  red. 

The  bases,  or  electro-positive  binary  compounds,  are  always 
formed  by  the  combination  of  a  metal  with  a  metalloid,  as  the 
protoxide  of  potassium  (potassa),  the  protosulphide  of  potassium, 
and  the  protoxides  of  iron,  copper,  and  silver. 

344,  Oxysalts.  —  A  large  majority  of  all  known  acids  and 
bases  are  oxides,  called  oxacids  and  oxybases;  and  the  salts 
formed  by  their  union  are  therefore  called  oxysalts.  They  are 
therefore  double  oxides. 

The  metallic  oxides,  in  regard  to  their  disposition  to  combine 
with  each  other  as  acids  and  bases,  and  with  the  oxides  of  the 
metalloids,  to  form  salts  (as  suggested  by  Kegnault),  may  be 
divided  into  several  very  distinct  classes,  as, 

1.  Basic  oxides,  "which  combine  readily  with  acids  and  form  definite, 
crystalizable  salts.  Most  of  them  are  protoxides,  as  potassa,  KO,  soda, 
NaO,  protoxide  of  silver,  AgO,  and  the  protoxide  of  iron,  FeO.  A  few 
are  sesqnioxides  or  suboxides. 

,  2.  A  cid  oxides,  which,  as  the  name  implies,  possess  acid  properties ; — 
they  combine  with  bases  to  form  salts,  and  very  generally  change  the 
blue  solution  of  litmus  to  red.  Most  of  them  are  bi-  or  teroxides,  as 
plumbic  acid,  PB02  (binoxide  of  lead),  chromic  acid,  Cr03,  and  man- 
ganic acid,  Mn03.  "Occasionally  they  are  still  higher  oxides,  as  per- 
manganic acid,  Mn207. 

3.  Neutral  oxides,  which  may  combine  with  either  acids  or  bases,  as 
alumina,  A120,,  and  the  sesquioxide  of  antimony,  Sb203 ;  or  with  neither, 
as  the  binoxides  of  silver,  potassium,  barium,  and  strontium.      Some 
of  these,  by  the  action  of  acids,  especially  if  heated,  are  decomposed. 

4.  Saline  oxides,  which  result  from  the  combination  of  a  basic  metallic 
oxide  with  a  higher  oxide  of  the  same  metal,  as  the  magnetic  oxide 
of  iron,  Fe304,  which  is  really  a  compound  of  the  protoxide,  acting  as  a 
base,  with  the  sesquioxide,  acting  as  an  acid ;  and  its  proper  formula  is 
therefore  FeO,Fe203.     The  oxides  of  manganese,  MngO^  and  of  chromium, 
O804,  furnish  other  examples. 

QUESTIONS. — Are  most  of  the  acids  formed  by  combinations  of  the 
metalloids  ?  Do  some  of  the  metals  form  acid  compounds  ?  How  do  the 
•acids  generally  affect  the  blue  solution  of  litmus  ?  Of  what  are  the  Dasea 
mostly  composed?  344.  What  is  said  of  a  majority  of  all  the  known 
acids  and  bases  ?  What  four  classes  of  metallic  oxides  are  mentioned  * 


SALINE   COMPOUNDS,    OR   SALTS.  293 

345.  Sulphur  Salts. — Two  sulphides  often  combine,  forming 
double  sulphides,  analogous  to  the  double  oxides.     They  possess, 
in  many  respects,  similar  characters  to  the  double  oxides  or  oxy- 
salts,  and  are  called  sulphur  salts. 

Some  of  the  principal  sulphur  bases  are  the  protosulphides  of 
potassium,  sodium,  lithium,  barium,  strontium,  calcium,  and  mag- 
nesium j  and  some  of  the  more  important  sulphur  acids  are  the 
sulphides  of  arsenic,  antimony,  carbon,  tin,  gold,  and  hydrogen. 

The  sulphur  salts  generally  are  so  constituted  that  if  the  sul- 
phur they  contain  were  replaced  by  an  equivalent  quantity  of 
oxygen,  oxysalts  would  be  produced.  Thus,  the  carbosulphide 
of  potassium,  KS,CS2,  when  the 'sulphur  is  replaced  by  oxygen, 
becomes  carbonate  of  potassa,  KO,C02;  and,  in  like  manner,  the 
double  sulphide  of  potassium  and  arsenic,  KS,AsSe,  by  a  similar 
substitution,  becomes  arseniate  of  potash,  KO,As05. 

346.  Chlorosalts, — The  chlorosalts  are  double  chlorides,  one 
of  the   simple  chlorides  acting  as  a  chlorobase,  and  the  other 
as  a  chloroacid,  as  the  double   chloride  of  gold  and  potassium, 
KCl,AuCl3,  called  also   aurochlorate   of  chloride   of  potassium, 
and  platinochlorate  of  chloride  of  sodium,  NaCl,PtCl2. 

In  the  same  manner  two  iodides  (an  iodobase  and  an  iodoacid)  bro- 
mides, or  fluorides,  may  unite  to  form  in  each  case  a  series  of  salts 
analogous  to  the  preceding,  but  not  much  is  known  of  them. 

It  is  to  be  observed  that  these  combinations  take  place  only  between 
members  of  the  same  series,  as  oxides  with  oxides,  sulphides  with  sul- 
phides, &c. ;  it  is  evidently  possible  that  members  of  different  series  may 
unite,  as  an  oxide  with  a  chloride,  a  chloride  with  a  sulphide,  &c. ;  but 
it  is  a  question  not  fully  settled  whether  such  compounds  are  ever  really 
formed. 

347.  Haloid  Salts. — Besides  the  compounds  recognised  by  the 
above  remarks  as  salts,  the  binary  compounds  of  chlorine,  iodine, 
bromine,  and  fluorine  with  many  of  the  metals,  have  been  classed 
with  the  salts  by  Berzelius  and  other  eminent  chemists,  because 
of  their  resemblance,  in  many  of  their  properties,  to  the  salts, 

QUESTIONS.— 345.  What  are  sulphur  salts?  What  is  said  of  the  con- 
stitution of  the  sulphur  salts  ?  Give  an  example.  246.  What  are  chloro- 
salts? May  the  iodides,  bromides,  &c.,  form  similar  series  of  salts? 
Are  these  combinations  always  between  members  of  the  same  series? 
347.  What  are  haloid  salts,  so  called  ?  Are  these  compounds  salts,  accord- 
ing to  the  definition  of  a  salt  adopted  above  ? 
25* 


294  SALINE   COMPOUNDS,   OR   SALTB. 

properly  so  called.  To  distinguish  them  from  the  salts  proper, 
they  have  been  called  haloid  salts.  But  we  prefer  to  limit  the 
definition  of  a  salt,  as  given  above,  although  in  so  doing  we  of 
course  exclude  common  salt,  chloride  of  sodium,  from  the  class. 

The  elements,  chlorine,  iodine-,  &c.,  which,  by  combining  with  metals, 
form  the  so  called  haloid  salts,  combine  also  with  hydrogen,  forming 
acid  compounds  called  hydracids  (168),  as  the  hydrochloric,  hydriodic 
&c.  Now  when  powerful  hydrous  acids  are  brought  in  contact  with  the 
haloid  salts,  important  reactions  take  place,  dependent  upon  the  wate* 
of  the  acid.  Thus,  by  the  action  of  oil  of  vitriol  upon  chloride  of  potas- 
sium, we  obtain  sulphate  of  potassa  and  hydrochloric  acid,  as  shown  in 
the  following  equation : 

KC1  -f  S08,HO  =  KO,S03  +  HC1. 

Here  the  water  of  the  acid  is  decomposed,  yielding  its  oxygen  to  the 
potassium  to  form  potassa,  and  its  hydrogen  to  the  chlorine  to  form  hydro- 
chloric acid. 

So,  on  the  other  hand,  the  action  of  a  hydracid  on  an  oxybase  results 
in  the  production  of  a  haloid  salt  and  water.  Thus, 

KO  -f  HC1  =  KC1  +  HO. 

348.  Neutralization  of  Acid  and  Base. — When  an  acid  and 
base  combine  to  form  a  salt,  the  peculiar  and  characteristic  pro- 
perties of  each,  in  a  great  measure,  disappear,  the  new  compound 
formed  not  being  characterized  by  the  properties  of  either  of  its 
ingredients,  but  possessing  others  entirely  distinct.      Thus,  an 
acid  is  generally  sour  to  the  taste,  and  changes  vegetable  blues 
to  red,  but  the  salts  it  may  form  with  bases  possess  neither  of 
these  properties ;  so,  also,  the  alkalies  are  caustic  to  the  fles.h  and 
taste,  and  combine  with  oils  to  form  soaps,  but  the  salts  which 
they  form  with  the  acids  are  entirely  destitute  of  these  properties. 
Most  of  the  other  peculiar  properties  of  both  acids  and  bases, 
when  the  two  combine,  are  affected  in  the  same  manner,  and 
they  are  therefore  said  to  be  neutralized. 

349.  Salts  are  often  spoken  of  as  divided  into  the  three  classes  of 
neutral  salts,  super  or  acid  salts,  and  sub  or  basic  salts  ;  but  the  distinction 

QUESTIONS. — What  is  said  of  the  elements  chlorine,  iodine,  &c.,  which 
form  the  so-called  haloid  salts  by  combining  with  the  metals?  What 
reactions  take  place  when  powerful  hydrous  acids  act  upon  these  salts? 
Give  an  illustration.  348.  When  an  acid  and  base  combine  do  the  pecu- 
liar properties  of  each  disappear  ?  Give « some  further  illustration. 
349.  What  three  classes  of  salts  are  mentioned  ? 


SALINE   COMPOUNDS,    OR    SALTS.  295 

cannot  always  be  made  with  accuracy.  In  general,  a  neutral  salt  is 
formed  by  the  union  of  a  single  equivalent  of  the  acid  and  base,  while 
an  acid  salt  contains  two  or  more  equivalents  of  acid  to  one  of  base ;  and 
a  sub  or  basic  salt  contains  two  or  more  equivalents  of  base  to  one  of  acid. 
But  this  is  to  be  understood .  as  liable  to  many  exceptions.  Frequently 
salts  denominated  neutral  contain  as  many  equivalents  of  acid  as  there 
are  equivalents  of  oxygen  in  the  base.-  Thus,  the  neutral  sulphate  of 
soda  is  NaO,S03,  and  sulphate  of  the  protoxide  of  iron  FeO,S08,  but  the 
sulphate  of  the  peroxide  of  iron  is  Fe203,3S03. 

Some  few  acids  have  the  property  of  combining  with  bases  in  such  £ 
manner- that  one  equivalent  of  acid  will  hold  in  union  with  it  one,  two, 
three  (or  even  more)  equivalents  of  base,  and  yet  these  several  salts  are 
considered  as  neutral ;  such  acids  are  called  polybasic  acids.  Phosphoric 
acid  (282)  furnishes  an  instance  of  the  kind. 

350.  Solubility  and  Crystalization  of  the  Salts, — Nearly  all 
the  salts  are  solid  at  ordinary  temperatures,  and  very  many  of  them, 
are  susceptible  of  crystalization.  Very  generally  they  are  more 
soluble  in  warm  than  in  cold  water,  and  often  their  solubility 
increases  in  proportion  as  the  temperature  of  the  water  is  ele- 
vated. The  following  table  shows  the  quantity  of  nitrate  of 
potash  soluble  in  100  parts  of  water  at  several  different  tem- 
peratures : 

Temperatures.  Parts  soluble  in  100  parts  water. 

32°  13-3 

64°  , 29-0 

113°  74-6 

207°  236-0 

In  some  cases,  the  solubility  rapidly  increases  as  the  tempera- 
ture is  raised,  up  to  a  certain  point,  and  then  diminishes.  Sul- 
phate of  soda  (Glauber's  salt)  furnishes  an  instance  of  this  kind. 
Of  this  salt  100  parts  of  water,  at  32°,  take  up  12  parts ;  at  77°, 
99  parts; -at  91°,  322  parts; — but  above  this  temperature  the 
solubility  diminishes,  so  that  at  the  boiling  point  only  about  212 
parts  will  be  held  in  solution. 

QUESTIONS. — What  in  general  is  a  neutral  salt  ?  What  is  a  super  or 
acid  salt  ?  What  is  a  sub  or  basic  salt  ?  Do  salts  denominated  neutral 
often  contain  as  many  equivalents  of  acid  as  there  are  equivalents  of 
oxygen  in  the  base?  Give  an  example.  What  are  polybasic  acids? 
350.  Are  the  salts  usually  solid  at  ordinary  temperatures  ?  Are  they 
more  soluble  in  warm  or  cold  water?  What  is  said  of  the  solubility 
of  nitrate  of  potash  in  water  at  different  temperatures?  How  is  the 
solubility  of.  sulphate  of  soda  in  water  affected,  as  the  temperature  of  the 
water  is  raised? 


296  SALINE   COMPOUNDS,    OR   SALTS. 

Crystals  of  soluble  salts  may  generally  be  obtained  by  making 
a  saturated  solution  at  an  elevated  temperature  and  allowing  it,  to 
cool  slowly.  Thus,  a  saturated  solution  of  alum  at  100°  or  150°, 
on  cooling  deposits  beautiful  octahedral  crystals;  and  if  a  tree 
or  basket  made  of  copper  wire  is  placed  in  the  solution  when 
warm,  the  crystals  will  attach  themselves  to  it  in  various  posi- 
tions, presenting  a  very  beautiful  appearance. 

351,  Salts  soluble  in  water, — and  even  some  that  are  insoluble 
— often  retain  in  their  crystals-a  portion  of  water,  which  is  called 
water  of  crystalization.     Thus  sulphate  of  soda  in  crystals  con- 
tains JO  equivalents  of  water,  and  its  proper  formula  is  NaO,SO3 
+  10 HO.     This  is  the  case  however  only  when  the  crystalization 
takes  place  at  a  temperature  below  92°  or  93° ;  when  it  crys- 
talizes  at  a  higher  temperature  the  crystals  are  anhydrous. 

The  same  salt  will  often  combine  with  very  different  quantities 
of  water  when  deposited  from  its  solution  at  different  temperatures. 
Sulphate  of  protoxide  of  manganese,  crystalized  from  an  aqueous 
solution,  at  43°,  has  the  formula,  MnO,S03  +  7HO;  when  crys- 
talized between  43°  and  68°  its  formula  is  MnO,S03  -f  6HO; 
and  again  when  crystalized  between  68°  and  86°,  its  formula  is 
MnO,S03  +  4HO. 

When  a  salt  of  the  kind  last  mentioned  is  heated  in  the  open 
air,  it  gives  up  its  water  in  successive  portions,  as  the  tempera- 
ture is  raised.  Sometimes  the  last  equivalent  of  water  is  held  by 
a  much  stronger  force  than  the  rest,  and  can  be  driven  off  only 
by  a  red  heat,  and  then  an  entire  change  in  the  nature  of  the 
salt  takes  place.  The  water  in  such  a  case  is  called  constitutional 
water. 

352.  Sometimes  a  salt  in  a  dry  atmosphere  loses  a  part  or  all 
of  its  water  of  crystalization,  and  falls  to  powder ;  it  is  then  said 
to  effloresce.     Again,  some  salts  absorb  moisture  from  the  air,  and 
are  then  said  to  deliquesce.     Common  pearlash  (carbonate  of  pot- 

QUESTIONS. — How  may  crystals  of  salts  soluble  in  water  often  be  ob- 
tained? 351.  What  i-s  water  of  crystalization?  Give  an  illustration. 
Will  the  quantity  of  water  of  crystalization  often  depend  upon  the  tem- 
perature of  the  solutions  from  which  the  crystals  are  deposited  ?  What 
will  be  the  effect  when  a  salt  of  this  kind  is  heated  ?  352.  When  is  a 
salt  said  to  effloresce  ?  WThen  to  deliquesce  ? 


SALINE  COMPOUNDS,  OR  SALTS.  297 

ash)  is  an  instance  of  a  deliquescent  salt.     Left  in  the  open  air 
for  a  time,  it  will  absorb  sufficient  water  to  effect  its  solution. 

353.  Water  holding  a  salt  in  solution  invariably  has  a  higher 
boiling  point  than  pure  water.  The  following  table  shows  the 
boiling  points  of  saturated  solutions  of  several  of  the  salts. 

™  Boiling  M* 


Chlorate  of  potash  ...............  61-5  ..............................  220° 

Common  Salt  ......................  41-0  ..............................  227° 

Nitrate  of  potash  .................  335-0  ..............................  241° 

Nitrate  of  Lime  ...................  362-0  ..............................  304° 

But  the  steam  from  such  boiling  solutions,  as  it  escapes  into  the 
open  air  (omitting  any  regard  to  variations  of  atmospheric  pres- 
sure), will  always  be  of  the  same  temperature  of  212°. 

When  a  hydracid,  as  the  'hydrochloric,  HC1,  acts  upon  a  metal, 
as  zinc,  the  acid  is  decomposed,  and  a  chloride  of  the  metal  formed, 
the  hydrogen  being  set  free  ;  thus, 

Zn  -f  HC1  ='ZnCl  +  H. 

So  when  liquid  hydrochloric  acid  is  poured  upon  potash,  the 
reactions  are 

KO  +  HC1,HO  ==  KC1  +  HO  +  H. 

In  both  these  cases,  therefore,  as  will  be  seen  by  an  examination 
of  the  formulae,  the  particle  of  hydrogen  of  the  hydracid  has 
simply  been  displaced,  and  a  particle  of  metal  substituted.  Now 
all  the  oxyacids,  or  nearly  all,  —  at  least  in  their  active  state,  — 
contain  water,  as  the  sulphuric  acid,  S03,HO,  and  nitric  acid, 
N.OgHQ.  They  may  indeed  be  obtained  free  from  water,  as 
S03,  and  N05,  but  they  are  then  solid  and  quite  inert,  possessing 
none  of  the  active  properties  of  the  liquid  acids,  which,  however, 
they  immediately  assume  on  the  addition  of  water. 
The  reaction  between  zinc  and  oil  of  vitriol  is 

Zn  +  SOs,HO  =  ZnO,S03  +  H. 

QUESTIONS.  —  353.  What  is  said  of  the  boiling  point  of  water  holding  a 
salt  in  solution  ?  What  is  said  of  the  temperature  of  the  steam  formed  ? 
When  a  hydracid  acts  upon  a  metal  what  are  the  reactions  that  take 
place  ?  What  when  hydrochloric  acid  acts  upon  potash  ?  In  these  casea 
is  the  hydrogen  simply  replaced  by  the  metal?  Is  the  result  the  same 
when  the  hydrated  oxyacids  act  upon  the  metals  ?  Explain  by  reference 
to  the  action  of  sulphuric  acid  upon  zinc. 


298      SPECIAL  DESCRIPTION    OP   THE   METALS. — POTASSIUM. 

Now  as  hydrated  sulphuric  acid  only,  S03HO,  is  capable  of  acting 
upon  this  metal,  and  not  the  dry  acid  S03,  may  we  not  in  this 
case  also,  in  like  manner,  consider  the  metal  as  simply  replacing 
the  hydrogen  ? 

If  this  view  be  adopted,  as  it  has  been  by  some  eminent 
chemists,  then  it  is  required  that  the  formulae  of  the  hydrated 
acids,  the  sulphuric,  nitric,  &c.,  should  be  changed  accordingly, 
sulphuric  acid  being  not  S03,HQ,  but  S04,H,  or,  as  generally 
written,  H,S04.  So  also  nitric  acid  is  to  be  considered,  not 
N05,HO,  but  H,N06,  and  so  of  other  acids. 

We  shall  not  discuss  the  subject  further,  but  simply  give  the 
formulae  for  several  well  known  salts,  according  to  the  old  and 
generally  received  view,  and  also  according  to  the  new  view. 

Salts.  Common  Theory.  New  Theory. 

Sulphate  of  Soda NaO,S03 Na,S04. 

Sulphate  of  Zinc ZnO,SO, Zn,S04. 

Nitrate  of  potash KO,N05    K,N06. 

Chlorate  of  potash KO,C106   K,C106. 


Separate  Description  of  the  Metals. 

354.  The  classification  of  the  metals  adopted  in  this  work  has 
already  been  indicated  (342). 

/  GROUP  I. 

p                   *]  Metals,  the  protoxides  of  which  are  alkalies. — The  protoxides 

I  of  these  metallic  elements  are  very  soluble  in  water,  and 

I  possess  in  an  eminent  degree  the  peculiar  properties  denomi 

J  nated  alkaline  properties. 

POTASSIUM. 

Symbol,  K  (Kalium);  Equivalent,  39*2;  Density,  0-865. 

355.  History. — Potassium  was  first  obtained  by  Sir  H.  Davy 
in  1807,  from  potash,  which  is  the  protoxide  of  the  metal.     He 

QUESTIONS. — If  this  view  be  adopted,  how  should  the  formula  for  com- 
mon sulphuric  acid,  or  oil  of  vitriol,  be  written  ?  How  that  for  nitric 
acid  ?  354.  What  metals  are  included  in  the  first  group  ?  How  ar« 
they  characterized  V  355.  By  whom  was  potassium  discovered  ? 


POTASSIUM. 


299 


procured  it  by  subjecting  a  piece  of  caustic  potash,  slightly 
moistened,  to  the  action  of  a  powerful  galvanic  current,  when 
oxygen  made  its  appearance  at  the  positive,  and  the  metal  potas- 
sium at  the  negative,  electrode.  Previous  to  this  time,  potash 
and  the  other  alkalies  and  earths  had  been  considered  as  simple 
substances.  Potassium,  in  combination  with  oxygen  and  other 
bodies,  is  very  generally  diffused  in  the  rocks  and  soils  of  every 
place,  but  is  never  found  in  nature  in  a  separate  state.  It  is 
contained  in  most  vegetable  and  many  animal  substances. 

356.  Preparation. — This  metal  is  best  prepared  by  heating 
intensely  dry  carbonate  of  potash  mixed  intimately  with  half  its 
weight  of  fine  charcoal-powder  and  iron  filings.  The  potash, 
being  an  oxide  of  potassium,  at  a  high  temperature  yields  its 
oxygen  to  the  charcoal  and  irqn,  and  itself  distils  over  into  a 
receiver  prepared  for  the  purpose.  ^ 

The  following  apparatus  answers  well  for  the  operation.  A  com- 
mon mercury  bottle, 

A,  covered  with  an 
infusible    lute,    and 
well  dried,  is  three- 
fourths     filled    with 
cream  of  tartar  that 
has  been  previously 
charred    and    mixed 
with    one-fourth    or 
one-fifth  of  its  weight 
of    pulverized    char- 
coal, and  placed  in  a 
proper  furnace,  with 
a  piece  of  gun-barrel, 

B,  about   a   foot  in 
length,     extending 
outward  and  connect- 

Jng  With  a  receiver,  C. Preparation  of  Potassium. 

QUESTIONS. — How  did  Sir  H.  Davy  procure  potassium?  How  were 
potash  and  the  other  alkalies  considered  previous  to  this  time  ?  Is  pot- 
ash very  generally  diffused  in  nature?  356.  How  is  potassium  now 
usually  prepared  ?  What  is  the  effect  produced  by  the  charcoal  ?  De- 
Bcribe  the  apparatus  figured  in  the  margin,  and  the  mode  of  using  it. 


300  POTASSIUM. 

A  fire  of  hard  coal  is  then  kindled  in  the  furnace  (represented 
in  section  in  figure),  which  should  have  a  good  draft,  by  con- 
necting with  a  chimney,  GrF,  of  sufficient  height,  in  order  to 
produce  the  greatest  heat  possible;  and  the  metallic  potassium, 
as  it  is  liberated  in  the  gaseous  state,  escapes  through  the  iron 
tube,  B,  and  is  condensed  and  collected  in  the  bottom  of  the 
receiver,  C.  In  this  receiver  some  naphtha  is  placed,  to  project 
it  from  the  atmosphere. 

Charred  cream  of  tartar  is  used  because  it  furnishes  an  inti- 
mate mixture  of  carbon  and  carbonate  of  potassa,  but  instead 
of  it  dry  carbonate  of  potash  (pearlash)  may  be  mixed  intimately 
with  half  its  weight  of  pulverized  charcoal. 

The  receiver,  C  (seen  in  section),  is  best  made 
\o  of  sheet  copper,  in  two  parts,  M  and  N,  the  upper 
part,  N,  being  without  a  bottom,  and  fittiog  accu- 
rately into  th£  lower  part,  M.     The  upper  part,  N, 
c  is  also  divided  into  two  parts  by  a  vertical  partition, 
as  shown  in  figure  j  it  is  also  provided  with  two 
tubulures,  o  and^,  directly  opposite-each  other,  the 
one,  o,  to  receive  the  end  of  the  gun-barrel,  B  (in 

Prep. of  Potassium.  ^    firgt    Qf   ^  aooompanying    figures)7   and    the 

other,  p  (corresponding  to  E  in  the  first  figure),  to  allow  the 
insertion  of  an  iron  wire  to  remove  the  obstructions  that  will 
occasionally  collect  in  the  gun-barrel  leading  from  the  iron  bottle. 
A  small  opening  is  also  made  for  this  purpose  in  the  partition 
of  the  receiver,  N. 

During  the  operation  much  incondensible  gaseous  matter  passes 
over  and  escapes  by  a  tube  of  glass  (shown  in  the  first  figure) 
provided  for  the  purpose ;  and  as  it  is  necessary  that  the  receiver 
should  be  kept  cold,  a  small  stream  of  cold  water  is  made  to  fall 
upon  it  constantly,  which  is  prevented  from  entering  the  lower 
part,  M,  by  a  rim  of  metal  passing  round  it,  as  shown  in  the 
figures.  The  tubulure,  p,  is  to  be  kept  closed  by  a  cork,  except  as 
it  is  necessary  to  remove  it  for  a  moment  to  insert  the  iron  wire, 
when  obstructions  occur  in  the  gun-barrel. 

The  potassium,  after  the  action  has  ceased,  will  be  found  in 
irregular  masses  in  the  naphtha  at  the  bottom  of  the  receiver ; 

QUESTION. — Where  will  the  potassium  be  found  ? 


BINARY    COMPOUNDS   OP  POTASSIUM.  301 

but  it  will  not"  be  pure.  It  is  now  collected  in  a  bag  of  cloth, 
through  which  it  is  squeezed  by  compressing  the  bag  with  pincers 
while  held  in  a  cup  of  warm  naphtha.  If  necessary,  it  may  be 
further  distilled  in  a  small  iron  retort. 

357.  Properties. — Potassium  is  a  solid,  in  color  and  lustre 
much  resembling  lead.  At  150°  it  melts,  and  at  a  dull  red  heat 
may  be  distilled  in  vessels  void  of  gases  capable  of  combining  with 
it.  It  is  the  lightest  metal  known,  having  a  density  of  only 
0-865,  and  floats  upon  the  surface  of  water.  At  ordinary  tem- 
peratures it  is  soft  like  wax,  but  at  32°  it  becomes  quite  hard. 
But  its  most  characteristic  property  is  its  affinity  for  oxygen ; — 
when 'thrown  upon  the  surface  of  water  it  absorbs 
the  oxygen  so  rapidly  as  to  be  inflamed,  and  burns 
with  a  beautiful  rose-colored  flame.  In  the  open 
air,  the  freshly-cut  surface  absorbs  oxygen  so 
rapidly  as  to  be  tarnished  instantly ;  and  heated 
even  in  carbonic  acid  (303),  it  takes  fire  and  burns  combustion  of 
by  absorbing  the  oxygen.  In  consequence  of  its  Potassium  upon 
affinity  for  oxygen  it  can  be  preserved  only  in 
tubes  hermetically  sealed,  or  under  some  liquid  that  does  not 
contain  .oxygen,  as  naphtha,  which  is  found  to  answer  the  pur- 
pose well. 


Binary  Compounds  of  Potassium. 

358.  Protoxide  of  Potassium— KO ;  eq.,  (39-2  +  8  =)  47-2. 
— This  is  potash,  or  potassa,  and  is  always  formed  when  the 
metal  is  exposed  in  the  open  air,  or  oxygen  gas,  or  acted  on  by 
water.    -In  the  latter  case,  the  potash  formed  is  immediately  dis- 
solved by  the  water,  as  will  be  found  by  applying  the  usual  tests. 
,  Pure  potash  is  a  white,  inodorous  substance,  with  a  pungent, 
,  caustic  taste,  and  very  soluble  in  water.     It  absorbs  carbonic  acid 


QUESTIONS. — 357.  Describe  some  of  the  properties  of  potassium.  What 
is  said  of  its  affinity  for  oxygen  ?  What  is  the  effect  when  a  small  piece 
of  it  is  thrown  upon  water?  How  is  it  preserved?  Why  is  naphtha 
selected  for  this  purpose  ?  358.  What  is  the  common  name  for  protoxide 
of  potassium  ?  Describe  potassa  ?  Does  it  usually  contain  water  ? 
26 


302 


BINARY  COMPOUNDS    OF   POTASSIUM. 


and  water  rapidly  from  the  air,  and  should  therefore  be  kept  in 
'close  bottles. 

When  prepared  by  the  slow  oxydation  of  potassium  in  dry  air 
or  oxygen  gas  it  is  anhydrous,  but  when  formed  by  the  oxydatiou 
of  the  metal  in  water,  or  from  any  of  its  salts,  it  is  always  in  the 
state  of  a  hydrate. 

Potash  forms  with  water  two  compounds,  the  monohydrate, 
KO,HO,  and  the  pentahydrate,  KO,5HO;  the  former  of  which 
is  the  caustic  potash  of  commerce.  To  prepare  it,  pearlash  (car- 
bonate of  potash)  is  dissolved  in  ten  times  its  own  weight  of 
water,  and  half  its  weight  of  recently-slaked  lime  mingled  with 
it,  in  successive  portions,  and  the  whole  boiled  briskly  for  half  an 
jiour.  It  is  then  allowed  to  settle,  and  the  clear  liquid  is  'drawn 
off.  The  lime,  in  this  process,  decomposes  the  carbonate  of 
potassa,  and  forms  insoluble  carbonate  of  lime,  which  settles  to 
the  bottom ;  and  the  clear  liquid  contains 
nearly  pure  potassa.  This  may  be  pre- 
served for  use  in  well-closed  bottles,  or  it 
may  be  evaporated  to  dryness  in  a  vessel 
of  such  a  form  as  not  to  allow  any  con- 
siderable accession  of  air.  To  insure  per- 
fect purity,  it  must  be  again  dissolved  in 
absolute  alcohol,  and  the  solution  filtered  and 
evaporated  as  before.  The  hydrate  is  soluble 
in  alcohol,  which  is  not  the  case  with  sul- 
phate of  potash,  usually  present  in  pearlash, 
or  carbonate,  portions  of  which  may  have 
escaped  decomposition  by  the  lime. 

359,  To  prevent  the  absorption  of  car- 
bonic acid  from  the  air  while  filtering,  an 
apparatus  like  that  figured  in  the  margin  is 
used.  It  consists  of  two  vessels,  A  and  D, 
of  equal  capacity,  and  connected  with  each 
Filtering  Apparatus.  other.  The  throat  of  the  upper  vessel  or 

QUESTIONS. — What  hydrates  of  potash  are  mentioned?  How  is 
pure  caustic  potash  prepared  from  the  carbonate?  Why  should  it  be 
dissolved  in  alcohol  and  filtered?  359.  Describe  the  mode  of  filtering 
the  alcoholic  solution. 


BINARY   COMPOUNDS    OP   POTASSIUM. 

funnel,  A,  is  obstructed  by  a  piece  of  coarse  linen  loosely  rolled  up, 
and  not  pressed  down  into  the  pipe  through  which  the  solution  is 
filtered.  The  pipe,  c,  extending  from  e  to  6,  serves  for  the  air  to 
pass  from  the  lower  vessel  to  the  upper  j  and  the  operation  goes 
quietly  on,  free  from  contact  with  the  atmosphere,  except  the  little 
contained  within  the  apparatus  at  the  beginning  of  the  process. 

Solution  of  potassa  is  highly  caustic,  and  its  taste  intensely 
acrid.  It  possesses  alkaline  properties  in  an  eminent  degree, 
converting  the  vegetable  blue  colors  to  green,  and  neutralizing 
the  strongest  acids.  It  absorbs  carbonic  acid  gas  rapidly,  and  is 
consequently  employed  for  withdrawing  that  substance  from  gase- 
ous mixtures. 

Potassa  is  employed  as  a  reagent  in  detecting  the  presence  of 
bodies,  and  in  separating  them  from  each  other.  The  solid  hydrate, 
owing  to  its  strong  affinity  for  water,  is  used  for  depriving  gases  of 
hygrornetric  moisture. 

Caustic  potash  attacks  all  animal  substances  with  avidity,  and 
neutralizes  all  acids.  With  the  fats  and  oils  it  combines  readily, 
forming  the  well-known  compound  called- soap,  of  which  we  shall 
have  occasion  to  speak  again  hereafter.  This  property  is  charac- 
teristic of  all  the  alkalies. 

The  pentahydrate  possesses  no  special  interest. 

360.  Peroxide  of  Potassium,  K03,  as  is  shown  by  the  formula, 
is  a  teroxide.     It  is  of  a  dull  yellow  color,  and  is  formed  by  burn- 
ing potassium  in  an  excess  of  dry  oxygen  gas.      Thrown  into 
water,  it  gives  up  two-thirds  of  its  oxygen,  and  solution  of  caustic 
potash  is  formed. 

361.  Chloride  of  Potassium,  KC1,  is  readily  obtained  by  neu- 
tralizing carbonate  of  potash,  KO,  C02,  by  hydrochloric  acid. 
The  reactions  which  take  place  have  already  (347)  been  explained. 
Like  common  salt  (chloride  of  sodium),  it  crystalizes  in  cubes, 
which  are  anhydrous. 

i.      Iodide  of  Potassium,  KI,  is  formed  by  heating  potassium  in 
contact  with    iodine;    or,   by  digesting   iodine    in   a   hot   solu- 

QUESTIONS. — What  is  said  of  the  action  of  potash  upon  animal  sub- 
stances? What  does  it  form  with  the  fats  and  oils?  360.  What  is 
peroxide  of  potassium?  361.  What  is  chloride  of  potassium?  How  is 
jodide  of  potassium  formed? 


304  SALTS    OF    POTASH. 

tion  of  caustic  potash,  and  exposing  the  mass,  when  dry,  to  a  red 
heat,  and  subsequently  crystalizing  from  solution  in  water  or 
alcohol.  It  is  a  white  solid,  very  soluble  in  water,  usually  seen 
crystalized  in  cubes,  and  is  often  sold  under  the  name  of  hydrio- 
date  of  potash. 

Solution  of  iodide  of  potassium  has  the  property  of  dissolving 
iodine,  and  becomes  of  a  brown  color;  it  also  dissolves  other 
iodides,  as  the  iodides  of  mercury. 

Iodide  of  potassium  is  much  used  in  medicine,  and  in  certain 
photographic  processes. 

Bromide,  KBr,  and  fluoride,  KF,  of  potassium,  like  the  chloride  and 
iodide,  crystalize  in  cubes. 

362.  Sulphides  of  Potassium. — There  are  at  least  five  sulphides  of  potas- 
sium, KS,  KS2,  KS3,  KS4,  and  KS5,  which,  as  shown  by  their  formulae, 
contain,  respectively,  1,  2,  3,  4,  and  5  equivalents  of  sulphur  in  combina- 
tion with  1  equivalent  of  the  metal. 

The  most  important  of  these  is  the  pentasulphide,  KS5,  which  is  easily 
prepared  by  heating  gently  a  mixture  of  carbonate  of  potash  and  sul- 
phur, or  by  boiling  a  solution  of  caustic  potash  with  an  excess  of  sulphur. 

It  is  a  yellowish-brown  solid,  very  soluble  in  water,  and  is  used  in 
medicine,  especially  in  cutaneous  diseases,  under  the  name  of  hepar 
sulphuris,  or  liver  of  sulphur.  The  tersulphide  is  also  used  in  the  same 
manner. 


Salts  of  Potash. 

363.  Carbonate  of  Potash,  KO,C02. — Carbonate  of  potash,  or 
pearlash  j  is  prepared  for  the  purposes  of  commerce  by  leaching 
the  ashes  of  forest  trees,  and  evaporating  the  lye  thus  obtained  to 
dryness,  and  then  heating  the  dry  mass  to  redness  for  a  time  in 
open  vessels,  to  burn  out  the  combustible  matter  which  is  con- 
tained in  it.  As  thus  procured,  it  is  a  white  spongy  mass,  very 
caustic  to  the  taste,  and  absorbs  moisture  rapidly  from  the  airj  so 
that  it  must  be  kept  in  close  vessels.  It  is  very  soluble  in  water, 
but  insoluble  in  alcohol,  and  is  easily  fused  at  a  red  heat.  That 
lound  in  commerce  is  very  impure,  being  mixed  with  silica  and 
o'her  substances.  It  is  manufactured  in  large  quantities  in  the 
United  States,  in  the  Canadas,  and  in  Russia. 

QUESTIONS. — What  use  is  made  of  iodide  of  potassium  ?  362.  What  is 
said  of  the  sulphides  of  potassium  ?  363.  What  is  pearlash  ?  How  is  it 
prepared  ?  Describe  it.  What  countries  furnish  it  in  large  quantities  ? 


SALTS    OF    POTASH.  305 

If  pure  carbonate  of  potash  is  required,  as  is  often  the  case  in 
the  laboratory,  the  tartrate  (cream  of  tartar)  or  oxylate  is  heated 
to  redness  in  the  open  air,  treating  the  charred  mass  thus  formed 
with  warm  water,  and  filtering.  The  solution  may  then  be  eva- 
porated to  dryness,  if  the  dry  salt  is  desired. 

By  slowly  evaporating  a  solution  of  carbonate  of  potash  the 
salt  may  be  crystalized,  though  not  without  difficulty. 

The  article  sold  as  potash  is  the  same  as  pearlash,  except  that 
it  is  not  subjected  to  the  last  process  of  calcination.  It  is  a  dark- 
colored  mass,  and  contains  much  caustic  potash,  as  well  as  car- 
bonate, and  is  used  extensively  for  the  manufacture  of  soap. 
Pearlash  is  employed  in  the  manufacture  of  glass  and  paints,  and 
for  various  other  purposes. 

364,  Bicarbonate  of  Potash,  KO,2C02.  —  This  salt  is  pre- 
pared by  subjecting  pearlash  in  solution,  for  some  time,  to  an 
atmosphere  of  carbonic  acid,  which  is  absorbed  in  large  quantity. 
Though  less  caustic  to  the  taste  than  pearlash^  it  is  still  highly  alka- 
line.    It  is  less  soluble  also  than  pearlash,  and  less  deliquescent. 

It  may  be  obtained  in  crystals  with  less  difficulty  than  the  car- 
oonate,  and  the  crystals  contain  a  single  equivalent  of  water. 
Their  formula  may  therefore  be  written  KO,C02  +  HO,C02, 
that  is,  the  salt  may  be  considered  as  a  double  carbonate  of  potash 
and  water. 

This  salt  is  extensively  used  under  the  name  of  salseratus. 

365.  Nitrate  of  Potash,  KO,N05. — This  salt,  the  saltpetre, 
or  nitre,  of  commerce,  is  formed,  in  this  country,  by  decomposing 
the  nitrate  of  lime,  which  abounds  in  the  caverns  of  some  of  the 
Western   StateSj  by  carbonate  of  potash,  and  filtering  and  eva- 
porating the  solution  thus  obtained.     In  some  parts  of  Europe  it 
is  prepared  in  nitre-beds,  which  are  made  by  heaping  together 
old  mortar,  refuse  animal  matter,  wood-ashes,  &c.,  in  which  it 
gradually  forms  by  the  action  of  the  atmosphere.     The  mass  is 

QUESTIONS. — How  may  pure  carbonate  of  potash  be  prepared  ?  What 
is  the  article  known  in  commerce  as  potash  ?  364.  How  is  bicarbonate 
of  potash  prepared  ?  May  it  be  obtained  in  crystals  ?  By  what  name  ifl 
it  familiarly  known  ?  365.  By  what  names  is  nitrate  of  potash  known  in 
commerce  ?  How  is  it  prepared  in  this  country  ?  How  in  some  parts 
of  Europe  ? 

26* 


306  SALTS    OF    POTASH. 

lixiviated  with  hot  water;  and  the  solution  by  evaporation  yields 
crude  nitre. 

Nitrate  of  potash  is  usually  seen  in  long  six-sided  prisms.  It 
is  a  colorless  salt,  of  a  cooling  saline  taste,  and  is  very  soluble  in 
water.  Its  density  is  about  1-93.  Heated  to  redness,  it  first 
melts  and  is  then  decomposed,  giving  off,  at  first,  pure  oxygen, 
and  afterwards,  if  the  heat  is  increased,  nitrogen  and  nitric  oxide. 
Thrown  on  burning  charcoal  it  is  decomposed,  producing  violent 
deflagration,  by  which  it  may  always  be  distinguished  from  sul- 
phate of  soda,  for  which  it  has  sometimes  been  mistaken.  It  is  a 
powerful  antiseptic,  and  is  used  with  common  salt  in  the  preserva- 
tion of  meat  and  other  substances. 

But  the  chief  use  of  nitre  in  the  arts  is  in  the  manufacture 
of  gunpowder,  which  is  composed  of  nitre  six  parts,  and  charcoal 
and  sulphur  each  one  part,  the  whole  being  moistened  and 
thoroughly  ground  together,  and  subsequently  pressed  and  granu- 
lated. When  fired,  the  nitre,  by  its  decomposition,  furnishes 
oxygen,  which  combines  the  carbon,  forming  carbonic  acid,  the 
sulphur  at  the  same  time  uniting  with  the  potassa.  The  action 
of  gunpowder  depends  upon  its  generating,  when  decomposed,  a 
large  quantity  of  gaseous  matter  at  a  high  temperature.  The 
gases  are  chiefly  nitrogen  and  carbonic  acid,  which,  at  the  moment 
of  explosion,  occupy  more  than  1000  times  the  volume  of  the 
powder  from  which  they  are  formed.  The  formation  of  the  gases 
is  not  instantaneous,  but  occupies  a  certain  time,  and  the  ball  is 
forced  from  the  gun  with  a  velocity  due  to  the  ultimate  effect 
of  the  whole. 

When  made  for  particular  purposes,  the  proportion  of  the  ingre- 
dients is  sometimes  considerably  varied.  We  may,  in  fact,  con- 
sider gunpowder  as  of  three  kinds,  which  may  be  called  sporting 
powder,  war  powder,  and  blasting  powder;  the  former  of  which 
is  required  to  detonate  more  rapidly  and  violently  than  either 
of  the  others.  The  composition  of  the  three  kinds  is  usually 
about  as  follows  : — 

QUESTIONS. — Describe  nitrate  of  potash?  How  does  heat  affect  it? 
What  is  the  effect  when  it  is  thrown  upon  burning  charcoal?  What 
uses  are  made  of  it?  What  is  the  composition  of  gunpowder  ?  What  are 
the  chemical  reactions  that  take  .place  when  it  is  fired  ?  Upon  what  doos 
the  action  of  gunpowder  depend  ?  What  different  kinds  are  mentioned  ? 


SALTS    OF    POTASH. 


307 


For  sporting  powder. 


For  war  powder 


.., Nitre 76-9  parts. 

Sulphur 9-6      " 

"^Carbon 13-5     " 

100-0     " 

...Nitre 75-0  parts. 

Sulphur 12-5     " 

Carbon 12-5     " 


For  blasting  powder.... 


100-0     " 

.Nitre 62-0  parts, 

Sulphur 20-0     " 

Carbon 18-0     " 

100-0     " 

Theoretically,  it  would  seem  that  the  best  proportion  would  be  1 
equivalent  of  nitre,  1  equivalent  of  sulphur,  and  3  equivalents  of  carbon. 
Thus,  - 

KO,N06  -fS-f3C  =  KS  +  N  +  3C02. 


The  proportion  by  weight  of  the  several  ingredients  would  then  be  as 
follows : — 

In  100  parts. 

Nitre,  1  equivalent 101-2... 74-85 

Sulphur,  1     «         16-0 11-84 


Carbon,    3 


18-0 13-31 


100-00 


This  is  very  nearly  the  same  proportion  as  that  given  for  war  powder 
above;  but  the  reactions  which  take  place  in  the  combustion  of  the 
powder  not  being  necessarily  the  same  precisely  as  indicated  in  the  above 
formula,  nor,  indeed,  in  any  two  cases  with  the  same  powder,  consider- 
able variation  in  the  proportion  of  the  ingredients  may  be  allowed.  For 
the  best  powder,  the  materials  should  be  freed  from  all  impurities  before 
using  them. 

366.  The  comparative  force  of  different  specimens  of  gunpowder,  or 
the  initial  velocity  a  given  quantity  of  it  will  communicate  to  a  ball  of  a 
given  weight,  is  determined  by  several  modes,  only  one  of  which,  called 
the  ballistic  pendulum  (see  figure  on  next  page),  will  be  described,  and 
that  very  briefly.  It  is  composed  of  two  parts,  the  ballistic  pendulum,  P, 
and  the  pendulum-gun,  G,  the  former  of  which,  P,  consists  of  a  conical  box, 
containing  a  mass  of  lead,  suspended  by  an  iron  rod,  in»the  manner  of  a 

QUESTIONS. — What  is  the  difference  in  the  composition  of  the  three 
kinds  of  gunpowder  ?  Is  the  composition  of  gunpowder  exactly  the  same 
as  would  seem  to  be  required  by  the  chemical  formula  ?  366.  How  is 
the  comparative  force  exerted  by  different  kinds  of  gunpowder,  when 
fired,  determined?  Describe  the  ballistic  pendulum. 


808 


SALTS    OF    POTASH. 


Ballistic  Pendulum. 


pendulum,  from  some 
very  firm  support.  G- 
is  a  common  gun-bar- 
rel supported  in  an 
frame,  which  is  also 
suspended  in  the  man- 
ner of  a  pendulum, 
the  gun-barrel,  when 
hanging  freely,  being 
made  to  point  to  the 
mass  of  lead.  At  m  n 
and  op  are  graduated 
arcs,  each  having  at- 
tached to  it  a  slider, 
which  is  carried  along 
with  the  movement  of 
the  rod  to  the  furthest 
point  to  which  it  oscil- 
lates, but  does  not  re- 
turn with  it. 

The  gun-barrel  is  now  charged  with  the  proper  quantity  of'the  powder 
to  be  tested,  and  the  ball  placed  in  it,  and  fired ;  and  the  ball  being 
projected  into  the  mass  of  lead  causes  it  to  move  to  the  left  (as  the  appa- 
ratus is  represented  in  the  figure)  to  a  certain  distance,  which  will  be 
exactly  shown  by  the  slide  upon  the  graduated  arc,  m  n.  At  the  same 
time  the  gun-barrel  will  recoil  to  the  right,  as  will  be  shown  by  the  slide 
upon  op:  The  initial  velocity  of  the  ball  may  now  be  calculated  from 
.the  distance  either  slide  has  traversed,  by  means  of  the  proper  mathe- 
matical formulae. 

To  insure  accuracy,  attention  must  be  paid  to  several  particulars  in 
the  adjustment  of  the  apparatus,  which  are  not  here  alluded  to. 

367.  Sulphate  of  Potash,  KO,S03. — This  salt  is  easily  pre- 
pared artificially  by  neutralizing  carbonate  of  potassa  with  sul- 
phuric acid;  and  it  is  procured  abundantly  by  neutralizing  with 
carbonate  of  potassa  the  residue  of  the  operation  for  preparing 
nitric  acid  (221).  Its  taste  is  saline  and  bitter.  It  generally 
crystalizes  in  six-sided  prisms,  bounded  by  pyramids  with  six 
sides,  but  its  primary  form  is  the  right  rhombic  prism.  The 
crystals  contain  no  water  of  crystalization,  and  suffer  no  change 
by  exposure  to  the  air.  They  decrepitate  when  heated,  and  enter 
into  fusion  at  a  red  heat.  They  require  16  times  their  weight 
of  water  at  60°,  and  5  of  boiling  water  for  solution. 


QUESTIONS. — 367.    How  may  sulphate   of  potash  be  prepared  arti- 
ficially ?     What  are  some  of  its  properties  ? 


SALTS    OP    POTASH. 


309 


368.  Bisulphate  of  Potassa,  KO,2S03,  is  easily  formed  by  ex- 
posing the  neutral  sulphate  with  half,  its  weight  of  strong  sulphuric 
acid  to  a  heat  just  below  redness,  in  a  platinum  crucible,  until  acid 
fumes  cease  to  escape.     It  has  a  strong  sour  taste,  and  reddens 
litmus  paper,  and  in  crystals  may  be  considered  a  double  sulphate 
of  potassa  and  water,  KO,S03-|-  HO,S03.    It  is  much  more  soluble 
than  the  neutral  sulphate,  requiring  for  solution  only  twice  its 
weight  of  water  at  60°,  and  less  than  an  equal  weight  at  212°. " 
It  is  resolved  by  heat  into  sulphuric  acid  and  the  neutral  sulphate. 

369.  Chlorate  of  Potash,  KO,C105.— This  salt  is  formed,  to- 
gether with  chloride  of  potassium,  by  passing  a  current  of  chlorine 
through  a  strong  solution  of  pearlash.      The  reactions  are  as 
follows : — 

6KO,C02  +  6C1  =  5KC1  +  KO,C106  +  6COZ. 

The  carbonic  acid  escapes  during  the  process,  and  the  chloride 
of  potassium  being  very  soluble  remains  in  solution,  while  the 
chlorate  crystalizes  in  shining  white  scales. 

The  chlorine,  before  entering  the  potash  solution,  should  be 
made  to  pass  through  a  three-necked  bottle  containing  a  little 


Preparation  of  KO,C10s. 


water,  to  separate  any  sulphuric  acid  which  may  pass  over  with 
it.     The  proper  arrangement  is  represented  in  the  figure. 

QUESTIONS. — 368.  How  is  bisulphate  of  potash  formed?     369.  Ho-w 
is  chlorate  of  potash  formed  ?     Describe  the  reactions  that  take  place. 


310  .          SODIUM. 

Its  taste  is  not  nnlike  that  of  nitre,  but  it  is  much  less  soluble 
than  that  salt.  Heated  moderately,  it  melts,  and  at  a  red  heat  is 
decomposed,  giving  up  the  whole  of  its  oxygen.  Thrown  on 
burning  charcoal,  it  deflagrates  like  nitre,  but  more  energetically. 
A  few  of  the  crystals,  wrapped  in  tin-foil,  with  a  piece  of  phos- 
phorus, or  a  little  sulphur,  explode  violently  by  a  blow  from  the 
hammer.  It  was  formerly  used  in  the  manufacture  of  Lucifer 
matches,  and  has  been  substituted  for  nitre  in  gunpowder;  which, 
however,  when  thus  prepared,  is  liable  to  explode  from  causes  so 
slight  that  its  manufacture  is  dangerous. 

The  silicates  of  potash  will  be  described  hereafter. 

370.  Sulphur-Salts  of  Potassium. — Protosulphide  of  potassium,  as  the 
electro-positive  element,  combines  with  many  other  electro-negative  sul- 
phides, forming  true  salts  (345),  but  we  shall  here  describe  only  the 
following  two : — 

Hydrosulphate  of  Potassium,  or,  more  properly,  the  hydrosulphate  of 
sulphide  of  potassium,  KS,HS,  is  prepared  by  passing  a  current  of  hydro- 
sulphuric  acid  (263)  through  a  solution  of  potash.  When  the  solution  is 
concentrated  the  salt  may  be  obtained  in  crystals. 

Carbosulphate  of  potassium,  KS,CS2,  may  also  be  crystalized.  It  ia 
prepared  by  pouring  bisulphide  of  carbon  into  an  alcoholic  solution  of 
protosulphide  of  potassium. 


SODIUM. 

Symbol,  Na  (Natron} ;  Equivalent,  23;  Density,  0-972. 

371,  History  and  Preparation, — Sodium  was  discovered  in 
1807,  by  Davy,  a  few  days  after  the  discovery  of  potassium, 
The  first  portions  of  it  were  obtained  by  means  of  galvanism; 
but  it  may  be  procured  in  much  larger  quantity  by  chemical  pro- 
cesses, precisely  similar  to  those  just  described  for  obtaining 
potassium.  Its  preparation  is  less  difficult  than  that  of  potassium. 

QUESTIONS. — Describe  the  properties  of  chlorate  of  potash.  What  is 
the  effect  when  it  is  thrown  on  burning  charcoal  ?  What  use  has  been 
made  of  it  ?  Why  may  it  not  be  used  in  the  formation  of  gunpowder  ? 

370.  How  is  hydrosulphate  of  potassium  formed?      What  is  its  com- 
position ?      What  is   the   composition   of  carbosulphato   of  potassium  ? 

371 .  How  is  sodium  prepared  ? 


BINARY     COMPOUNDS    OF    £  ODIUM.  311 

372.  Properties. — Sodium  has  a  strong  metallic  lustre,  and  in 
color  is  very  analogous  to  silver.  It  is  so  soft  at  common  tem- 
peratures, that  it  may  be  formed  into  leaves  by  the  pressure 
of  the  lingers. 

Sodium  soon  tarnishes  on  exposure  to  the  air,  though  less 
rapidly  than  potassium.  Like  that  metal  it  is  instantly  oxydized 
by  water,  hydrogen  gas  in  temporary  union  with  a  little  sodium 
being  disengaged.  When  thrown  on  cold  water,  it  swims  on  its 
surface  and  is  rapidly  oxydized,  though  in  general  without  in- 
flaming }  but  with  hot  water  it  scintillates,  or  even  takes  fire,  and 
burns  with  a  beautiful  yellow  flame,  which  readily  distinguishes  it 
from  potassium.  •  . 

By  throwing  two  pieces,  one  of  sodium  and  another  of  potas- 
sium, at  the  same  time,  into  a  vessel  of  water,  both  will  usually  be 
inflamed;  and  the  characteristic  colors  of  their  flames  will  be 
seen  together. 

Sodium  is  preserved  under  naphtha  in  the  same  manner  as 
potassium. 


Binary  Compounds  of  Sodium. 

373.  Protoxide  of  Sodium — NaO;  eq.,  (23  +  8  =)  31. — This 
compound,  usually  calle.d  soda,  is  formed  by  the  oxydation  of  sodium, 
as  potassa  is  from  potassium.  With  water  it  forms  a  solid  hydrate, 
which  is  easily  fusible,  and  very  soluble  both  in  water  and  alcohol. 
It  is  a  powerful  alkali,  and  very  similar  in  all  its  properties  to 
potassa.  Hydrate  of  soda  is  prepared  from  the  carbonate  in  the 
same  manner  as  the  hydrate  of  potash.  The  hydrate  is  known  as 
caustic  soda  ; — it  contains  a  single  equivalent  of  water,  and  its 

formula  is  therefore  NaO,HO. 

• 

Peroxide  of  Sodium,  Na08,  is  formed  by  burning  sodium  in  dry  air  or 
oxygen  gas. 

QUESTIONS. — 372.  Describe  the  properties  of  sodium.  What  is  the 
effect  when  it  is  thrown  upon  water  ?  How  is  it  preserved  ?  373.  What 
is  soda  ?  Describe  its  properties.  By  what  name  is  the  hydrate  of  soda 
known  ?  What  is  peroxide  of  sodium  ? 


312  BINARY.  COM  POUNDS    OF    SODIUM. 

374,  Chloride  of  Sodium— Nad;  eq.,  (23  +  354  =)  584.— 
This  is  the  common  salt  of  commerce.  It  may  be  formed  by 
burning  sodium  in  chlorine,  but  is  obtained  in  great  abundance 
as  a  solid  deposit,  called  rock  salt,  in  various  parts  of  the  world, 
as  in  England,  Poland,  and  at  Abingdon  in  Virginia ;  and  in 
solution  in  the  waters  of  brine  springs,  which  abound  in  New 
York,  Pennsylvania,  Virginia,  Kentucky,  Ohio,  and  other  States, 
as  well  as  in  other  countries.  Sea- water  contains  about  2-7  per 
cent,  of  this  substance,  while  the  water  of  the  great  salt  lake  in 
Utah  Territory  contains  about  20  per  cent.  Around  this  latter 
body  of  water  are  plains,  many  miles  in  extent,  which,  in  the  dry 
season,  are  covered  with  incrustations  of  very  pure  salt  to  the 
depth  of  more  than  half  an  inch.  In  the  rainy  season  it  is  more 
or  less  dissolved. 

Rock  salt  is  sometimes  mined  of  sufficient  purity  for  use,  and 
requires  only  to  be  pulverized ;  but  more  frequently  it  is  mixed 
with  clay  and  oxide  of  iron,  and  must  then  be  dissolved,  and  the 
pure  liquid  drawn  off  and  evaporated. 

In  'warm  countries,  as  on  the  coast  of  Portugal,  in  the  south 
of  France,  and  the  West  India  Islands,  this  substance  is  obtained 
by  the  spontaneous  evaporation  of  sea-water,  which  is  allowed,  on 
the  rise  of  the  tide,  to  flow  into  shallow  basins,  being4  passed 
from  one  to  another,  as  it  becomes  more  concentrated;  and 
finally,  the  evaporation  is  finished  by  means  of  artificial  heat. 

In  cold  countries,  as  on  the  borders  of  the  White  Sea,  the  pro- 
cess is  commenced  in  a  very  different  manner  : — the  sea-water  is 
exposed  to  the  cold  atmosphere,  by  which  a  large  part  of  the 
water  is  separated  in  the  form  of  ice,  and  the  remaining  liquid 
portion  is  drawn  off  and  evaporated. 

Pure  chloride  of  sodium  has  an  agreeably  saline  taste.  It  fuses 
at  a  red  heat,  and  becomes  a  transparent  brittle  mass  on  cooling. 
It  deliquesces  slightly  in  a  moist  atmosphere,  but  undergoes  no 
change  when  the  air  is  dry.  In  pure  alcohol  it  is  insoluble.  It 

QUESTIONS. — 374.  What  is  the  common  name  for  chloride  of  sodium? 
Where  is  it  found  in  the  solid  state  ?  What  are  brine  springs  ?  What  is 
the  proportion  of  it  contained  in  sea-water?  In  the  water  of  the  great 
salt  lake  in  Utah  Territory  ?  How  is  this  substance  procured  in  certain 
warm  countries  ?  How  in  certain  cold  countries  ?  Describe  some  of  the 
properties  of  common  salt  ? 


BINARYCOM POUNDS     OF     SODIUM.  318 

requires  twice  and  a  half  its  weight  of  water  at  60°  for  solution, 
and  its  solubility  is  not  increased  by  heat.     It  crystallizes  in 
cubes,  which  are  anhydrous,  and  have  a  density  of  about  2' 13  — 
when  its  solution  is  slowly  evaporated  in  the 
open  air  hopper-shaped  crystals,  as  figured 
in  the  margin,  are  of  common  occurrence. 
Their  formation  may  be  explained  as  fol- 
lows :— first  a  small  cubical  crystal  forms  at     Hopper-f^m  Crystal 
the  surface  of  the  solution,  which  tends  to 
sink  and  depress  the  surface,  as  shown  in  the  figure  A.     Soon 


Cryst.  Common  Salt. 

other  small  crystals  form  and  attach  themselves  to  the  first  one 
at  its  four  upper  horizontal  edges,  by  which  it  is  a  little  more  de- 
pressed, as  represented  in  the  figure  B ; 
a  further  addition  in  the  same  manner 
causes  a  further  depression,  as  seen  in  C, 

and  SO  On.  Cryst.  Common  Salt. 

A  saturated  solution  of  common  salt  does  not  freeze  even  at  0°, 
but  hydrated  crystals  are  formed  which  have  the  formula,  NaCl  + 
4HO.  It  fuses  at  a  red  heat,  and  may  even  be  sublimed  without 
change. 

The  uses  of  this  substance  are  well  known.  Besides  the  ordi- 
nary purposes  to  which  it  is  applied,  in  preserving  meat  from 
putrefaction,  and  in  seasoning  food,  it  is  used  extensively  in  the 
arts,  in  glazing  pottery-ware,  in  the  manufacture  of  bleaching- 
salt,  carbonate  of  soda,  hydrochloric  acid,  &c. 

The  name,  salt  (Lat.,  sal),  was  originally  given  to  this  sub- 
stance alone,  but  was  subsequently  extended  to  an  immense  class 
of  compounds  which  have  been  known  as  salts.  By  our  present 

QUESTIONS. — Describe  the  mode  in  which  hopper-formed  crystals  are 
sometimes  produced.  What  are  the  uses  of  this  substance?  Does  it 
belong  to  the  family  of  salts,  according  to  the  definition  of  the  werd 
which  we  have  adopted  ? 

27 


314  SALTS    OP     SODA. 

technical  arrangement  (347),  it  is  entirely  excluded  from  the 
class. 

Sodium  forms  definite  compounds  with  iodine,  bromine,  fluorine^ 
sulphur,  &c.,  but  they  are  not  described  in  this  work. 


Saks  of  Soda. 

375,  Sulphate  of  Soda,  NaO,S03.— Sulphate  of  soda,  or  Glau- 
ber's salt,  is  sometimes  found  native  in  dry  situations,  but  more 
frequently  in  solution  in  the  waters  of  mineral  springs.     It  is  also 
obtained  in  the  manufacture  of  hydrochloric  acid  (236).     It  was 
first  made  known  by  Glauber,  from  whom  it  received  its  name, 
although  he  himself  called  it  sal-mirabile.      It  has  a  cooling, 
saline,  and  somewhat  bitter  taste ;  and  is  very  soluble  in  water  at 
a  temperature  91°  or  92°,  but  less  so  in  water  that  is  very  cold 
or  very  hot  (350).     The  crystals  of  this  salt  usually  contain  more 
than  half  their  weight  of  water  of  crystalization,  which  escapes 
when  they  are  exposed  to  the  open  air,  and  they  crumble  into  a 
white  powder.     Their  proper  formula  is  NaO,S03+10HO.     The 
water  therefore  constitutes  nearly  56  per  cent.,  as  will  be  found 
by  making  the  calculation. 

Sulphate  of  soda  is  used  in  medicine  as  a  cathartic,  and  for 
the  preparation  of  the  carbonates  of  soda. 

Bisulphale  of  Soda  may  be  obtained  in  crystals  which  have  the  formula, 
NaO,2S09  -f  3HO.  Deprived  of  its  water  of  crystalization,  it  may  be 
used  in  preparing  anhydrous  S03  (259). 

376.  Hyposulphite  of  Soda,  NaO,S202. — This  salt,  which  is  much  used 
in  the  daguerreotype  process,  for  removing  the  sensitive  coating  from  the 
silver  plate,  after  being  taken  from  the  mercurial  vapor  bath,  is  prepared 
by  first  passing  a  current  of  sulphurous  acid  gas  through  a  solution  of  car- 
bonate of  soda,  to  form  sulphite  of  soda,  and  then  dissolving  sulphur  in  a 
concentrated  hot  solution  of  the  sulphite. 

It  mjay  be  obtained  in  crystals,  which,  according  to  some,  contain  5, 
and  according  to   others,   10  equivalents  of  water.      It  is  also  called 
*  dilhionate  of  soda. 

QUESTIONS. — 375.  What  is  Glauber's  salt?  What  are  some  of  its  pro- 
perties? What  is  said  of  its  water  of  crystalization?  What  use  is 
made  of  it  ?  376.  What  use  is  made  of  hyposulphite  of  soda  ? 


SALTS     OF     SODA. 


315 


377.  Carbonate  of  Soda,  NaO,C02. — The  carbonate  of  soda 
of  commerce  was  formerly  obtained  by  lixiviating  the  ashes  of 
sea-weeds,  in  the  same  manner  as  the  carbonate  of  potassa  is 
obtained  from  the  ashes  of  land-plants.  But  it  is  now  manu- 
factured altogether  from  .common  salt,  which  is  first  converted 
into  sulphate  of  soda  by  sulphuric  acid,  and  then  the  sulphate, 
mixed  with  charcoal  and  carbonate  of  lime,  is  heated  intensely  in 
a  wind-furnace. 

The  materials,  which  consist  of  about  2  parts  of  the  anhydrous 
sulphate,  2  parts  of  chalk  (carbonate  of  lime),  and  1  of  charcoal, 
are  well  ground  together,  and  in- 
troduced upon  the  hearth,  H  H, 
of  a  reverbatory  furnace,  similar 
to  that  represented  in  section  in 
the  figure ;  and  by  continued  action 
of  the  heat,  carbonate  of  soda, 
NaO,C02,  oxysulphide  of  calcium, 
CaS,CaO,  and  carbonic  oxide,- CO, 
are  formed  : — the  latter  compound 
being  gaseous,  of  course  passes  off. 
The  oxysulphide  of  calcium  being 
insoluble  in  water,  it  is  now  only 
necessary  to  digest  the  black  mass  which  comes  from  the  furnace 
in  warm  water,  and  filter,  and  a  solution  of  carbonate  of  soda  is 
obtained.  This  is  now  evaporated  to  dryness.  It  may  be  obtained 
in  crystals,  which  always  contain  much  water  of  crystalization, 
and  effloresce  in  dry  air.  It  is  the  sal  soda  of  commerce. 

The  mixture  as  taken  from  the  furnace  is  the  soda  ash,  or 
British  barilla  of  commerce,  and  has  been  sometimes  used  as  a 
manure.  , 

Carbonate  of  soda  is  extensively  used  in  the  manufacture  of 
glass  and  hard  soap,  and  for  other  purposes. 

Sesqnicarfoonate  of  Soda,  2NaO,3C02,  called  trona,  is  found  in  the 
•waters  of  certain  lakes  in  Egypt,  in  Hungary,  and  in  this  country  in 
springs  among  the  Rocky  Mountains. 


Preparation  of  Carbonate  of  Soda. 


QUESTIONS. — 377.  From  what  was  carbonate  of  soda  formerly  obtained? 
How  is  it  now  manufactured  ?     Describe  the  process. 


316  8  ALTS     OF     SODA. 

378.  Bicarbonate  of  Soda,  NaO,2C02.—  This  salt  is  formed  by 
exposing  the  carbonate  in  solution  to  an  atmosphere  of  carbonic  acid, 
in  the  same  manner  as  the  bicarbonate  of  potash.     Like  the  cor- 
responding salt  of  potash,  it  always  contains  one  atom  of  water, 
and  may  be  considered  a  double  carbonate  of  soda  and  water, 
according  to  the  formula,  NaO,C02  +  H'0,C02.     It  is  often  used 
by  bakers  as  a  substitute  for  sal-aeratus. 

379.  Biborate  of  Soda,  NaO,2B03. — This  salt  occurs  in  solu- 
tion in  the  waters  of  certain  lakes  in  Thibet  and  the  East  Indies, 
from  which  it  is  obtained  by  evaporation,  and  was  formerly  im- 
ported into  this  country  and  England  under  the  name  of  tincal. 
When  refined,  by  solution  and  recrystalization,  it  is  sold  as  borax, 
a  substance  well  known  for  its  extensive  use  in  the  arts  in  various 
metallurgic  operations.     At  present,  most  of  the  borax  of  com- 
merce is  obtained  from  Tuscany,  where  it  is  prepared  by  adding 
carbonate  of  soda  to  the  native   boracic  acid  (826)  of  the  hot 
springs  which  abound  in  an  extensive  volcanic  district  of  th.it 
country.     To  obtain  it  pure,  several  recrystalizations  are  required. 

Ordinary  borax  crystalizes  in  right  rhombic  prisms,-  which  con- 
tain 10  equivalents  of  water ;  but  when  crystal] zed  from  a  hot 
solution  the  crystals  are  octahedrons,  and  contain  only  5  atoms 
of  water. 

When  borax  is  heated,  it  first  loses  its  water  of  crystalization, 
which  causes  it  to  froth  up  very  much ;  and  at  a  red  heat  fuse& 
into  a  clear  transparent  liquid,  which  on  cooling  has  the  appear- 
ance of  glass.  At  high  temperatures,  it  dissolves  most  of  the 
metallic  oxides,  and  becomes  colored. 

Borax  is  used  as  a  flux  in  metallurgic  operations,  in  the  pre- 
paration of  certain  kinds  of  glass,  and  in  medicine. 

380.  Nitrate  of  Soda,  NaO,N05,  resembles  nitrate  of  potassa 
in  many  of  its  properties,  but  cannot  be  substituted  for  it  in  the 
manufacture  of  gunpowder,  because   of  its  tendency  to  absorb 

QUESTIONS. — 378.  What  is  bicarbonate  of  soda  ?•  What  use  is  made 
of  it  ?  379.  Where  is  biborate  of  soda  obtained  ?  What  is  it  often 
called  ?  Where  is  most  of  the  borax  of  commerce  obtained  at  the  pre- 
sent time  ?  What  use  is  made  of  it  ?  380.  For  what  is  nitrate  of  sod\ 
used? 


SALTS    OF    SODA.  317 

moisture  from  the  atmosphere.  It  is  used  instead  of  nitrate  of 
potash  in  the  preparation  of  nitric  acid,  and  sometimes  as  a 
manure. 

381.  Phosphates  of  Soda. — Phosphoric  acid  forms  with  soda 
(and  the  bases)  three  series  of  salts,  viz.,  tribasic  or  ordinary 
phosjrfiates,  bibasic  or  pyrophosphates,  and  monobasic  or  mcta- 
phosphates,  corresponding  to  the  three  states  (282)  of  the  acid. 

'  I.  Tribasic  Phosphate  of  Socfa. — Of  this  there  are  three  va 
rieties,  viz. :  1.  The  salt,  3NaO,P05.  2.  The  salt,  (2NaO  + 
110)  P05.  3.  The  salt,  (NaO  +  2HO)  P05.  The  three  varieties 
are  tribasic,  but  the  base  of  the  first  consists  of  3  eq.  of  soda ;  the 
base  of  the  second  of  2  eq.  of  soda  and  1  eq.  of  water;  the  base 
of  the  third  of  1  eq.  of  soda  and  2  eq.  of  water.  The  water  serving 
as  base  in  such  salts  is  called  basic  water. 

The  first  two  varieties  usually  crystalize  with  24  eq.  of  water, 
and  the  third  with  2  eq.  of  water.  If  heated,  they  readily  give 
up  their  water  of  crystalization,  but  a  red  heat  is  required  to 
expel  the  basic  water.  All  of  them  in  solution  give  a  yellow 
precipitate,  3AgO,P06,  with  solution  of  nitrate  of  silver. 

II.  Bibasic  Phosphate  of  Soda — Pt/rophosphate  of  Soda. — 
This  compound  furnishes  two  varieties,  viz.,  1.  The  salt,  2NaO,PO5; 
2.  The  salt,  (NaO  +  HO)  P05.     Both  varieties  are  bibasic,  but  the 
base  of  the  first  consists  of  2  eq.  of  soda,  and  that  of  the  second  of 
1  eq.  of  soda  and  1  eq.  of  water.      Bibasic  phosphate  of  soda 
crystalizes  with  10  eq.  of  water; — the  solution  of  both  varieties 
gives,  with  nitrate  of  silver,  a  white  precipitate,  2AgO,P05. 

III.  Monobasic  Phosphate  of  Soda — Metdphosphate  of  Soda 
— NaO,F05. — This  phosphate  in  solution  gives  a  white  precipitate 
with  solution  of  nitrate  of  silver,  AgO,P05;  but  its  composition, 
it  will  be  observed,  differs  from  that  procured  from*the  bibasic 
phosphate.     Solution  of  this  phosphate  also  has  the  property  of 

QUESTIONS. — 381.  What  is  said  of  the  salts  formed  with  soda  by  phos- 
phoric acid  ?  What  varieties  of  tribasic  phosphate  of  soda  are  there  ? 
How  may  they  bo  tested  when  in  solution  ?  What  varieties  of  bibasic 
phosphate  of  soda  are  there  ?  What  is  said  of  the  precipitate  they  give 
with  nitrate  of  silver  f  What  is  metaphosphate  of  soda  ? 
27* 


818  LITHIUM. 

coagulating  the  whites  of  eggs,  an  effect  not  produced  by  the 
other  phosphates. 

For  the  methods  of  preparing  these  varieties  and  sub-varieties 
of  phosphate  of  soda,  the  inquiring  student  will  consult  larger 
works  on  this  science,  especially  the  excellent  one  of  Regnault ; 
the  object  of  the  present  work  not  permitting  so  much  minute 
detail. 

With  other  bases  phosphoric  acid  probably  forms  similar  series 
of  salts,  but  the  subject  has  not  been  fully  investigaged. 

382.  Characteristics  of  Potash  and  Soda  Salts. — All  the  salts  of  potash 
and  soda  that  are  soluble  are  distinguished  from  other  metallic  salts, 
except  the  salts  of  lithia,  which  are  very  rare,  by  giving  no  precipitate 
with  solutions  of  the  alkaline  carbonates.  It  is  therefore  sufficient, 
practically,  to  be  able  to  distinguish  between  these  two  classes  of  salts ; 
for  which  the  following  tests  will  suffice. 

With  tartaric  acid  potassa  forms  a  sparingly  soluble  salt,  which,  if  the 
solution  is  moderately  concentrated,  appears  as  a  white  precipitate ;  but 
with  soda  no  precipitate  is  formed,  as  the  corresponding  salt  of  soda  is 
very  soluble. 

With  potash  a  strong  solution  of  chloride  of  platinum  forms  a  yellow 
precipitate,  the  double  chloride  of  potassium  and  platinum,  which  be- 
comes more  copious  by  the  addition  of  alcohol ;  but  in  the  same  circum- 
stances no  precipitate  is  formed  by  the  salts  of  soda,  because  of  the 
solubility  of  the  double  chloride  of  platinum  and  sodium. 


LITHIUM.' 
Symbol,  lj ;  Equivalent,  6- 4 ;  Density,  —  ? 

383.  History,.  Etc.  —  Lithium  is  a  very  rare  substance,  and  is  found 
only  in  a  few  minerals,  as  spodumeme,  and  the  variety  of  mica  called 
lepidolite.  It  is  obtained  from  these  in  combination  with  oxygen  as  the 
protoxide,  lilhia.  From  this  the  metal  may  be  procured  with  some  diffi- 
culty by  means  of  galvanism.  It  is  a  white  metal,  like  sodium.  The 
protoxide,  lithia,  is  a  powerful  alkali,  like  potash  or  soda,  but  is  less 
soluble  The  name  is  from  the  Greek,  lithos,  a  stone,  in  allusion  to  the 
source  from  which  it  is  obtained. 

The  salts  of  lithia,  heated  before  the  blowpipe,  give  a  red  tinge  to  the 
flame. 

QUESTIONS. — 382.  How  are  the  soluble  salts  of  potash  and  soda  dis- 
tinguished from  other  salts?  Describe  the  mode  of  distinguishing  a 
soluble  salt  of  potash  from  one  of  soda  by  means  of  tartaric  acid.  By 
means  of  solution  of  chloride  of  platinum.  383.  What  is  said  of  lithium? 
From  what  is  the  name  derived  ? 


AMMONIUM.  319 


Ammonium,     (Not  IsolaUe.') 

384.  History,  Etc. — This  name  is  given  to  a  supposed  com- 
pound of  nitrogen  and  hydrogen,  NH4,  which  has  never  yet  been 
obtained  in  a  separate  state,  but  is  believed  by  many  to  enter 
into  the  composition  of  most  of  the  ammoniacal  compounds,  and 
to  possess  in  some  respects  the  characters  of  a  metal.  Its  symbol 
is  written  NH4,  or  Am.  \ 

When  strong  aqua  ammonias  (225),  in  contact  with  a  little 
mercury,  which  is  connected  with  the  negative  electrode  of  the 
galvanic  battery,  is  subjected  to  the  action  of  a  strong  electrical 
current,  ozygen  is  liberated  at  the  positive  electrode  and  the  mer- 
cury increases  very  much  in  volume,  and  becomes  less  fluid, 
having  the  consistency  of  butter  or  soft  lard,  but  still  retains 
perfectly  its  metallic  lustre.  This  has  very  much  the  character 
of  an  amalgam ;  and  we  may  suppose  that  under  the  influence 
of  the  current,  ammonium,  NH4  (equal  to  NH3  -f  H)  has  been 
formed  from  the  ammonia  and  the  hydrogen  of  the  water,  and  at 
once  united  with  the  mercury,  the  oxygen  escaping  at  the  other 
electrode. 

The  same  compound  may  also  be  obtained  simply  by  com- 
bining a  little  potassium  or  sodium  with  50  or  100  times  its 
weight  of  mercury,  and  pouring  on  it  a  strong  solution  of  sal 
ammoniac,  NH3,HC1.  In  this  case  the  reaction  seems  to  be 

KHg  +  NH3,HCl  =  KCl+NH4,Hg. 

This  compound,  called  ammoniacal  amalgam,  when  removed 
from  the  solution  in  which  it  was  formed,  rapidly  undergoes 
spontaneous  decomposition,  yielding  ammonia  and  hydrogen  in  the 
proportion  of  2  volumes  of  the  former  and  1  volume  of  the  latter. 
After  a  little  time  the  mercury  alone  is  found  entirely  unchanged. 

QUESTIONS. — 384.  What  is  the  compound  to  which  the  name  ammo- 
nium is  given  ?  Has  it  been  obtained  in  a  separate  state  ?  What  is  the 
mode  of  preparing  ammoniacal  amalgam  by  the  xise  of  the  galvanic  bat- 
tery? Explain  the.  reactions  by  which  we  may  suppose  the  new  sub- 
stance to  be  produced.  Describe  the  mode  of  producing  it  by  the  use 
of  sal  ammoniac  in  solution.  ,What  are  the  reactions  that  appear  to  take 
place  ?  What  is  the  effect  when  the  amalgam  is  removed  from  the  solu- 
tion ?  What  are  obtained  when  it  decomposes  ? 


320  BINARY   COMPOUNDS   OF   AMMONIUM. 

If  this  amalgam  is  subjected  to  a  temperature  of  32°,  it  crys- 
talizes  in  cubes,  and  its  decomposition  is  retarded. 

Although  this  compound,  NH4,  which  has  received  the-  name 
of  ammonium,  has  not  been  obtained  in  a  separate  state,  its 
existence  in  combination  with  other  bodies  would  seem  to  be 
established ;  and  also  its  peculiar  metallic  character.  It  is  capable 
of  replacing  potassium  and  sodium  in  combination,  and  is  there- 
fore isomorphous  with  them. 

Ammonia,  NH3,  has  heretofore  (224)  been  described.  It  has 
been  called  volatile  alkali,  because  of  its  reactions  with  other 
substances,  and  especially  with  the  acids,  being  the  same  as  those 
of  the  other  alkalies,  the  protoxides  of  potassium,  sodium,  and 
lithium.  We 'introduce  the  subject  again  for  the  purpose  of 
describing  some  of  its  more  important  compounds,  which  we 
shall  do  according  to  this  ammonium  theory,  as  it  is  called; 
because  it  affords  us,  in  the  present  state  of  our  knowledge,  the 
most  simple  and  lucid  view  of  this  important  class  of  bodies  that 
can  be  presented.  But,  at  the  same  time,  it  should  always  be 
kept  in  mind  that  the  existence  of  ammonium,  NH4,  even  in  com- 
bination with  other  substances,  is  not  to  be  considered  as  fully 
determined. 


Binary  Compounds  of  Ammonium. 

385.  Protoxide  of  Ammonium,  NH40,  or  AmO. — As  is  the 
case  with  ammonium,  the  existence  of  this  compound  is  hypo- 
thetical. But  all  the  ammonia  salts  of  oxygen  acids,  contain  an 
atom  of  water  in  their  composition,  which  appears  to  be  essential 
to  their  existence.  This  atom  of  water,  combined  with  the  am- 
monia, NH3,  forms  the  compound  in  question,  protoxide  of  ammo- 
nium, NH40,  which  unites  with  the  acid  to  form  the  salt.  Thus, 
the  composition  of  nitrate  of  ammonia,  as  formerly  supposed,  is 
NH3,N05,HO,  which  evidently  is  the  same  as  NH40,N05,  except 
as  to  the  mode  of  the  arrangement  of  the  particles. 

QUESTIONS. — How  is  this  amalgam  affected  by  a  cold  of  32°  ?  What  is 
said  of  the  relation  of  ammonium  to  potassium  and  sodium  ?  Why  has 
ammonia  been  called  volatile  alkali  ?  885.  What  is  said  of  protoxide 
»f  ammonium  ? 


SALTS    OP    AMMONIA.  321 

As  ammonium  is  isomorphous  with  potassium  and  sodium,  so 
this  compound  is  isomorphous  with  potash  and  soda,  which  it  is 
capable  of  replacing  in  many  of  their  compounds. 

386,  Chloride  of  Ammonium,  NH4C1. — This  is  the  compound 
often  called  sal-ammoniac,  and  hydrochlorate  of  ammonia.  If  it 
be  considered  as  a  proper  hydrochlorate  of  ammonia,  its  formula 
of  course  will  be  NH3,HC1. 

It  may  be  obtained  by  neutralizing  carbonate  of  ammonia  by 
hydrochloric  acid ;  but  for  use  in  the  arts  it  is  procured  from  the 
liquor  obtained  in  the  distillation  of  bones,  in  preparing  animal 
charcoal,  and  also  from  that  which  condenses  in  the  manufacture 
of  coal-gas.  The  latter  affords  it  in  large  quantities. 

Sal-ammoniac  is  a  white  solid,  very  tough,  and  difficult  to 
pulverize,  and  has  a  density  of  about  145.  It  has  a  pungent, 
saline  taste,  and  is  very  soluble  in  water;  and  sublimes  without 
fusion  at  a  temperature  below  redness.  Triturated  with  recently- 
slaked  lime,  it  yields  ammonia,  which  is  easily  recognised  by  its 
pungent  odor.  It  is  used  for  various  purposes  in  the  arts  and  in 
medicine. 


Salts  of  Ammonia. 

387.  Carbonates  of  Ammonia, — There  are  several  carbonates 
of  ammonia.  The  one  best  known  is  the  sal-volatile  of  the  shops, 
which  is  a  sesquicarbonate.  It  is  a  semi-transparent  solid,  which 
is  very  soluble  in  water,  and  has  the  pungent  odor  of  ammonia. 
Its  composition,  on  the  "  ammonium  theory,"  is  2NH40,3C02; 
but  considered  without  reference  to  this  theoryj  its  formula  is 
usually  written  2NH3,3C024-2HO.  By  long  exposure  to  the  air 
it  is  converted  into  a  bicarbonate,  NH4O,2C02  -f  HO. 

Besides  these,  there  is  also  a  neutral  carbonate  of  ammonia. 

Sulphate  of  Ammonia,  NH40,S03. — Sulphate  of  ammonia  is 
a  soluble  salt,  isomorphous  with  sulphate  of  potassa.  It  is  some- 

QUESTIONS. — Is  ammonium  isomorphous  with  potassium  and  sodium  ? 
386.  What  is  sal-ammoniac  ?  How  is  it  obtained  ?  Describe  its  pro- 
perties. 387.  What  carbonates  of  ammonia  are  mentioned?  Describe 
sulphate  of  ammonia. 


322  SILICATES   OF  POTASH  AND   SODA — GLASS. 

<4 

times  found  in  the  lava  of  volcanos,  and  may  be  formed  artificially 
by  saturating  aqua  ammonise  or  solution  of  carbonate  of  ammonia 
with  sulphuric  acid.  It  is  sometimes  used  as  a  manure. 

Nitrate  of  Ammonia,  NH3,N05  +  HO,  or,  as  it  is  now  con- 
sidered, nitrate  of  oxide  of  ammonium,  NH40,N05,  is  prepared 
by  neutralizing  nitric  acid  with  ammonia,  or  its  carbonate.  It  IB 
a  white  salt,  very  soluble  in  water,  and  destitute  of  any  arnmo- 
niacal  odor.  It  is  used  in  preparing  nitrous  oxide  (215). 

388.  Phosphate  of  Soda  and  Ammonia,  (NaO,NH40,HO)P05.— This  is 
the  compound  called  microcosmic  salt,  and  much  used  as  a  flux  in  blow- 
pipe operations.  Its  crystals  contain  8  eq.  of  water  of  crystalization, 
which  is  given  up  at  a  very  moderate  heat ;  and,  at  a  high  temperature, 
both  the  basic  water  and  ammonia  are  expelled,  and  the  very  fusible 
metaphosphate  of  soda  only  remains. 

It  is  prepared  by  dissolving  in  2  parts  of  hot  water  6  or  7  parts  of  phos- 
phate of  soda,  and  then  adding  1  part  of  sal-ammoniac.  On  cooling,  tho 
salt  in  question  crystalizes,  while  chloride  of  sodium  remains  in  solution. 

389.  Hydrosulphate  of  Sulphide  of  Ammo- 
nium, NH4S,  HS. — This  compound,  it  will  be 
observed,  is  a  sulphur  salt  (345),  being  com- 
posed of  two  sulphides,  sulphides  of  ammo- 
nium and  hydrogen.  It  is  prepared  by  pass- 
ing a  current  of  hydrosulphuric  acid  through 
aqua  amrnonige,  which  is  to  be  kept  cool 
during  the  operation.  The  apparatus  repre- 
sented in  the  figure  will  answer  for  the 
purpose. 

It  is  much  used  in  the  laboratory  as  a  test 
Preparation  of  NH<S,HS.  for  several  of  the  metals. 


Silicates  of  Potash  and  Soda — Glass. 

390,  Silica,  or,  more  properly,  silicic  acid,  combines  at  high 
temperatures  with  the  alkalies  angl  earths  apparently  in  indefinite 
proportion,  producing  compounds  which  at^very  high  temperatures 
are  more  or  less  liquid,  but  at  a  lower  heat  have  a  pasty  con- 
sistency, and  when  cold  are  hard,  uncrystaline,  and  more  or  less 

QUESTIONS. — 388.  What  use  is  made  of  phosphate  of  soda  and  am- 
monia ?  How  is  it  prepared  ?  389.  How  is  hydrosulphate  of  sulphide 
of  ammonium  prepared  ?  To  what  class  of  salts  does  it  belong  ?  390.  How 
is  silica  made  to  combine  with  the  alkalies  and  earths?  What  is  said  of 
the  compoun  is  produced  ? 


SILICATES    OF   POTASH   AND    SODA  —  GLASS.  323 

transparent.  All  these  compounds  are  known  under  the  name 
of  glass. 

There  are  several  kinds  of  glass,  all  of  which  are  double  sili- 
cates of  potassa  and  soda,  or  one  of  these  with  silicate  of  lime, 
lead,  magnesia,  baryta,  alumina  or  iron,  but  the  proportions  are 
variable. 

Silicic  acid  has  no  action  upon  the  bases  at  ordinary  tempera- 
tures, but  it  readily  combines  with  them  in  a  state  of  fusion,  or 
with  their  carbonates;  in  the  latter  case  of  course  expelling  the 
carbonic  acid. 

391,  When  silica  is  fused  with  2  or  3  times  its  own  weight 
of  carbonated  potash  or  soda,  a  compound  is  formed  which  is 
soluble  in  hot  water,  and  has  been  called  soluble  glass,  or  liquor 
silicum.     The  solution,  when  applied  to  wood  and  other  com- 
bustible substances,  soon  dries  and  forms  a  transparent  coating 
which  protects  them  from  the  air  and  renders  them  less  combustible 
when  exposed  to  great  heat. 

If  the  proportions  are  reversed,  and  2  parts  of  silica  and  1  part 
of  carbonate  of  potash  or  soda  are  used,  a  proper  glass  is  formed, 
which  is  quite  insoluble  in  water,  and  nearly  all  acids. 

The  proportions  of  the  ingredients  in  the  different  varieties 
of  glass  are  exceedingly  variable,  but  common  window,  or  crown 
glass,  is  always  a  mixture  of  silicate  of  potash  or  soda  and  lime. 

Crystal,  or  flint  glass,  is  a  silicate  of  potash  or  soda  and  oxide 
of  lead;  it  is  softer  than  other  kinds,  and  more  fusible  and 
dense,  and  therefore  better  adapted  for  optical  purposes.  When 
a  thread  of  it  is  heated  in  the  flame  of  a  lamp,  it  is  blackened  by 
the  reduction  of  the  oxide  of  lead. 

392,  Bohemian  glass,  which  is  very  infusible,  contains  only 
silicate  of  potash  and  lime.     It  is  much  used  in  the  manufacture 
of  chemical  apparatus. 

The  finest  kinds  of  glass  are  made  only  of  the  purest  materials ; 
but  impure  materials,  containing  alumina  and  the  oxides  of  iron 
and  manganese,  answer  for  such  glass  as  that  of  which  green  bottles 
are  made. 

QUESTIONS. — What  is  glass?  391.  How  is  soluble  glass  formed?  Of 
what  is  crystal  glass  composed  ?  392.  What  is  said  of  Bohemian  glass  ? 


321  SILICATES   OP   POTA6H   AND   SODA  —  GLASS. 

Though,  as  above  stated,  glass  is  considered  insoluble  in  water  and  the 
acids,  except  such  as  contain  fluorine  (252),  yet  certain  varieties  of  it  are 
sometimes  attacked  by  acids,  solutions  of  the  alkalies,  or  of  their  car- 
bonates, and  even  by  pure  water,  especially  at  a  boiling  temperature. 
Glass  that  has  been  a  long  time  buried  in  the  earth,  is  sometimes  found 
with  a  pearly  incrustation  upon  its  surface,  in  consequence  of  the  separa- 
tion of  its  alkalies ;  and  is  sometimes  quite  soft,  so  as  to  be  cut  with  a 
knife. 

All  these  different  varieties  of  glass  have  a^density  varying  from  2-4  to 
3-7,  but  glass  may  be  made  of  a  density  as  high  as  5-4. 

Enamel,  used  for  various  purposes,  and  especially  for  watch 
and  clock  faces,  is  made  of  silica  and  potash,  or  soda  and  oxide 
of  lead,  and  rendered  opake  by  oxide  of  tin. 

Colored  glass  is  made  by  adding  to  any  of  the  varieties  metallic 
oxides,  as  those  of  cobalt,  copper,  manganese,  antimony,  gold,  &c. 
A  white  opake  glass,  in  imitation  of  porcelain,  is  made  by  adding 
to  the  glass  when  in  fusion  arsenious  acid. 

393.  Manufacture  of  Glass.  —  The  materials  for  glass  are 
first  to  be  fused  together,  at  a  high  temperature, 
and  in  such  a  manner  that  no  impurities  from  the 
smoke  of  the  fire  or  other  source  shall  be  mixed 
with  it.  This  is  done  by  using  pots  made  of  fire- 
clay, and  entirely  enclosed  within  the  walls  of  the 
furnace,  except  the  projecting  mouth.  The  figure 
in  the  margin  represents  the  section  of  one,  with  its 
opening  or  mouth  towards  the  left  hand.  Usually 
several  are  placed  in  a  circle  in  the  same  furnace,  and  heated  by 
the  same  fire. 

The  principal  instrument  used  is  an  iron  tube  or  pipe,  four  or 
five  feet  in  length  ',- — one  end  of  this 
being  dipped  into  the  melted  glass, 
which  has  now  the  consistency  of 
soft  wax,  a  portion  adheres  to  it,  and 
is  removed  from  the  pot.  As  its 

Glass  Operations— Marver 

shape  is  irregular,  it  is  first  rolled 
on  an  iron  plate,  called  a  marver  (see  figure),  to  give  it  a  cylin- 

QUESTIONS. — Is  glass  entirely  insoluble  in  water  and  the  acids?  Of 
what  is  enamel  made?  How  is  colored  glass  formed?  393.  Describe 
briefly  the  mode  of  manufacturing  window  glass. 


SILICATES   OF   POTASH   AND   SODA  —  GLASS. 


325 


drical  form,  and  is  then  blown  into  a  pear-shape  (as  seen  in  figure 
A),  by  forcing  air  through  the  pipe  from  the  lungs.  As  the  glass 
is  still  soft,  to  prevent  it  from  inclining 
in  one  direction  or  another,  as  it  would 
inevitably  if  held  still  for  a  moment,  it 
is  kept  constantly  whirling,  by  rolling 
the  pipe  in  the  hands."  If  held  in  the 
position  A,  the  hollow  mass  will  gra- 
dually become  elongated,  and  if  inverted 
and  held  in  the  position  B,  the  upper 
part  sinks,  and  it  takes  the  form  here 
seen; — of  course,  in  any  particular  case,  the  workman  will  be 
guided  in  the  mode  of  handling  by  a  regard  to  the  form  which  he 
wishes  to  give  it.  As  rapid  cooling  is  constantly  taking  place, 
the  glass  has  to  be  re-heated  frequently,  which  is  done  by  holding 
it  in  a  heated  furnace  provided  for  the  purpose. 

For  common  window  glass,  the  mass  in  the  form  of  B,  being 
re-heated  to  soften  it,  is  held  by  the  rod  with  the  glass  down- 
ward, and  swung  backward  and  forward  in  the  manner  of  a  pen- 
dulum, until  it  is  sufficiently  elongated,  and  has  the  form  C ; — 


Glass  Blowing. 


Preparation  of  Window  Glass. 

by  this  time  it  has  partially  cooled,  and  by  holding  the  extreme 
point  a  little  time  in  the  furnace  it  is  softened  so  that  a  blast  of 
air  from  the  lungs  is  forced  through  it,  and  an  assistant  with 
shears  accurately  removes  the  lower  part,  giving  it  the  form  D. 
The  cylindrical  part  is  now  to  be  separated  from  the  rod  by  a 
section  around  the  upper  part,  as  shown  in  E,  and  subsequently  a 
longitudinal  fracture  is  made  in  the  hollow  cylinder  thus  obtained 
28 


326  SILICATES   OP  POTASH   AND   SODA  —  GLASS. 

through  its  whole  length ;  and  it  now  only  remains  to  open  the 
cylinder  thus  prepared  in  order  to  reduce  it  to  a  perfect  plane. 
This  is  doee  by  softening  it  in  a  proper  furnace  and  pressing  the 
part  gently  with  an  iron  rod,  as  represented  in  the  figure. 


Preparation  of  Window  Glass. 

394.  The  variety  of  window  glass  called  crown  glass  is  pre- 
pared in  a  different  mode.     The  melted  mass  taken  from   the 
melting-pot  is  first  blown  into  the  form  of  a  globe,  and  then  an 
iron  rod  attached  to  it  on  the  side  opposite  that  to  which  the  tube 
adheres,  and  the  tube  separated  by  applying  a  little  cold  water. 
This,  of  course,  leaves  an  opening,  which  becomes  enlarged  by 
softening  in  the  heating  furnace,  and  giving  it  a  rapid  rotary 
motion  by  means  of  the  iron  rod  held  in  the  hand.     By  heating 
it  several  times  in  this  way,  the  rapid  rotary  motion  being  con 
tinued,  the  globe  is  at  length  opened  out,  and  becomes  a  circular 
disc,  which,  after  the  proper  annealing,  is  cut  into  panes  by  a 
diamond. 

395,  Many  articles  now  made  of  glass,  are  blown  in  metallic 
moulds  prepared  for  the  purpose,  or  are  pressed  between   two 
moulds,  one  of  which  shuts  into  the  other,  so -as  to  give  the 
proper  shape.     This  is  called  pressed  glass. 

Plate  ylass,  used  for  mirrors  and  for  large  windows,  is  poured, 
when  in  a  state  of  fusion,  upon  a  plahe  surface,  and  a  roller 
passed  rapidly  over  it,  to  reduce  it  to  the  proper  thickness.  The 
surfaces  are  then  ground  down  to  a  perfect  plane  by  means  of 

QUESTIONS. — 894.  How  is  crown  glass  manufactured  ?  395.  Describe 
the  mode  of  forming  articles  of  pressed  glass.  Describe  the  mode  of 
forming  plates  for  mirrors. 


SILICATES   OF  POTASH   AND   SODA  —  GLASS.  327 

friction  with  sand  and  fine  emery,  and  then  finely  polished  by 
friction  with  colcothar,  or  red  oxide  of  iron. 

Small  articles  of  glass  may  readily  be  made  of  glass  t^be  before 
a  blowpipe,  which  is  blown  by  a  bellows  worked  by  the  foot.  The 
best  fuel  to  be  used  is  burning  fluid,  consisting  of  four  parts  of 
strong  alcohol  and  one  part  of  camphene  \  but  oil  or  tallow  will 
answer.  A  very  little  experience  will  enable  one  to  bend  even 
quite  large  glass  tubes,  and  to  perform  many  other  operations" 
of  great  importance  in  the  laboratory. 

All  articles  made  of  glass,  if  suddenly  cooled,  are  exceedingly 
brittle,  and  liable  to  fracture  from  the  slightest  causes,  even 
trifling  changes  of  temperature.  They  are  therefore  annealed  by 
placing  them  in  a  furnace  prepared  for  the  purpose,,  and,  after 
becoming  quite  hot,  are  allowed  to  cool  very  slowly.  By  this 
means  such  a  change  is  produced  in  the  molecular  arrangement 
of  the  particles,  that  this  tendency  to  fracture  is  much  diminished. 

Articles  of  glass  that  have  not  been  annealed,  sometimes  break  in  a 
singular  manner ; — a  tumbler  half  filled  with  liquid,  and  grasped  by  the 
hand,  will  break  quite  around  at  the  surface  of  the  water  by  the  slight 
heat  of  the  hand ;  or  a  thick  glass  tube  several  inches  in  length  will  split 
through  its  whole  length  simply  by  being  wet,  especially  if  merely  touched 
by  a  hard  substance,  as  a  piece  of  wire.  Occasionally,  after  being  handled 
and  laid  aside,  they  break  spontaneously. 

398.  The  Bologna,  or  philosopher's  vial,  is  made  in  the  form 
of  an  ordinary  vial,  but  with  thicker  sides  and  a  very  thick 
bottom,  and  is  not  annealed.  A  smart  blow  may  be  given  to 
it  by  a  piece  of  lead  or  of  wood,  or  a  leaden  shot  dropped 
into  it,  without  producing  any  effect ;  but  by  dropping  into 
it  a  small  angular  piece  of  flint,  it  almost  invariably  falls  to 
pieces.  Sometimes  even  coarse  sand  will  produce  this  effect. 
In  this,  and  in  the  following  case,  the  result  is  due  to  the 
want  of  annealing. 

Prince  Rupert'*  drops  are  simply  drops  or  tears  of  glass, 
which  are  made  by  allowing  the  glass  when  melted  to  drop 
from  the  end  of  a  rod  into  water,  by  which  they  are  sud- 
denly cooled.  They  are  perfectly  solid,  but  when  the  small 
end  is  broken  off,  the  whole  mass  falls  to  powder,  with  a 
slight  explosion. 

QUESTIONS.— Why  are  all  articles  made  of  glass  annealed  before  using? 
What  is  likely  to  be  -the  effect  if  the  process  is  omitted  ?  396.  Describe 
the  Bologna  vial.  What  are  Prince  Rupert's  drops  ? 


328  BINARY    COMPOUNDS    O'F    BARIUM. 


GROUP  II. 

f- 

BARIUM  ~\  Metals,  the  protoxides  of  which  are  alkaline  earths. — These 
STRONTIUM  1  latter  are  called  baryta,  strontia,  lime,  and  magnesia.  They 
CALCIUM  |  possess  the-  same  properties  which  characterize  the  alka- 
MAGNESIUM  J  lies,  but  in  less  degree. 

BARIUM. 

Symbol,  Ba;  Equivalent^  68-5;  Density,  —  ? 

397.  History,  Etc. — This  metal  is  procured  by  passing  vapor 
of  potassium  over  baryta  (exide  of  barium)  at  a  red  heat,  or  by 
passing  the  galvanic  current  through  hydrate  of  baryta  in  contact 
with  mercury,  the  latter  forming  the  negative  electrode  of  the 
battery.  The  amalgam  thus  obtained  is  carefully  heated  in  a 
glass  tube  through  which  a  current  of  dry  hydrogen  is  constantly 
passing,  and  the  mercury  expelled.  The  barium  will  be  left  in 
small  globules.  It  has  the  color  and  lustre  of  silver,  and  melts 
at  a  red  heat,  but  is  not  easily  volatilized.  In  the  air  it  is  rapidly 
oxydized,  and  when  heated  burns  with  a  red  flame.  It  is  also 
rapidly  oxydized  when  thrown  into  water.  Its  name  is  from  the 
Greek  barns,  heavy;  its  compounds  generally  possessing  this 
characteristic  property. 


Binary  Compounds  of  Barium. 

398.  Protoxide  of  Barium,  BaO;  eq.,  (68-5  +  8=)  74-5. — 
This  compound  has  been  known  many  years  as  barytes  or  baryta. 
It  may  be  obtained  by  decomposing  nitrate  of  baryta  by  heat/ 
which  is  best  done  by  using  an  earthern  retort  in  a  furnace  (as 
represented  in  the  figure  on  next  page),  and  applying  the  heat  as 
bng  as  gaseous  matter  is  evolved. 

QUESTIONS. — What  metals  are  included  in  the  second  group  ?  What 
do  their  protoxides  form  ?  Do  these  earths  possess  alkaline  properties  ? 
397.  How  is  barium  procured  ?  How  is  the  metal  affected  in  the  air  ? 
From  what  circumstance  or  property  is  the  name  derived  ?  898.  How 
may  the  alkaline  earth,  baryta,  be  obtained  ? 


SAL'TS  OF  BARYTA. 


829 


Baryta  is  a  gray  powder,  which 
slakes  like  lime  when  water  is  poured 
upon  it,  and  becomes  very  hot.  It 
dissolves  readily  in  water,  but  is  less 
soluble  than  potash  or  soda — a  pro- 
perty by  which  the  alkaline  earths 
are  distinguished  from  the  alkalies. 
It  is  very  caustic  to  the  taste,  and 
affects  vegetable  colors  in  the  same 
manner  as  the  alkalies. 

Peroxide  of  Barium,  Ba02. — This 
oxide  may  be  formed  by  passing  a  cur-- 
rent of  dry  oxygen  gas  over  baryta,  at 
a  low  red  heat ;  or  by  simply  heating 
baryta  in  an  atmosphere  of  oxygen.  It  is  used  only  for  the  pur- 
pose of  preparing  peroxide  of  hydrogen  (206). 

Chloride  of  Barium,  Bad;  eq.,  (68-5  +  354  =)  103-9.— 
This  compound  is  formed  by  dissolving  the  native  carbonate  of 
baryta  in  diluted  hydrochloric  acid,  and  by  other  modes.  It 
crystalizes  in  white  scales,  which  contain  two  atoms  of  water. 
It  is  very  soluble  in  water,  and  is  much  used  as  a  test  for  sul- 
phuric acid,  with  which  baryta  forms  an  insoluble  sulphate 


Preparation  of  Baryta. 


and 


Salts  of  Baryta. 

399.  Carbonate  of  Baryta,  BaO,C02,  is  found  native, 
sailed  witherite  by  mineralogists.  From  it  all  the  other 
of  baryta  may  be  prepared. 

Sulphate  of  Baryta,  BaO,S03. — Sulphate  of  baryta  is  found 
abundantly  in  various  places,  often  in  beautiful  crystals.  It  has 
a  density  of -about  44,  and  is  insoluble  in  water.  When  pow- 


QUESTTONS. — Describe  the  properties  of  baryta.  Describe  the  mode 
of  preparing  peroxide  of  barium.  How  is  chloride  of  barium  formed  ? 
For  what  purpose  is  it  used  ?  399.  Is  carbonate  of  baryta  found  native? 
What  is  said  of  the  occurrence  of  native  sulphate  of  baryfa? 

28* 


330        BINARY    COMPOUNDS    OF    'STRONTIUM. 

dered  and  mixed  with  charcoal,  and  heated  intensely,  it  is  con- 
verted into  sulphide  of  barium,  from  which  the  other  salts  of 
baryta  may  be  prepared,  as  from  the  native  carbonate.  By 
mineralogists,  it  is  called  heavy  spar,  because  of  its  great  weight. 
Ground  to  a  fine  powder,  it  is  used  as  a  substitute  for  white  lead, 
either  alone  or  mixed  with  white  lead.  All  the  soluble  com 
.  pounds  of  baryta  are  poisonous. 

Nitrate  of  Baryta,  BaO,N05.  —  This  salt  of  baryta  is  prepared  by 
digesting  the  native  carbonate,  or  the  sulphide,  obtained  as  just  de- 
scribed, in  nitric  acid.  Its  only  use  is  in  certain  chemical  analyses,  and 
in  procuring  the  earth  baryta. 


STRONTIUM. 
Symbol,  Sr;  Equivalent,  44;  Density,  —  ? 

400.  History,  Etc.  —  Strontium  is  obtained  from  its  oxido, 
strontia,  in  the  same  manner  as  barium ;  and  in  its  appearance 
it  is  said  very  much  to  resemble  that  metal.     Like  barium,  also, 
it  decomposes  water  with  the  evolution  of  hydrogen,  and  oxydizes 
rapidly  in  the  open  air.     It  receives  its  name  from  Strontian,  a 
village  in  Scotland,  near  which  it  was  first  obtained. 

Binary  Compounds  of  Strontium. 

401.  Protoxide  of  Strontium,  SrO;  eq.,  (44  +  8=)  52.— 
This  compound,  which  is  the  earth  strontia,  is  formed  by  the 
oxydation    of  strontium.      It    is  prepared   also   by   heating  the 
nitrate  of  strontia  to  redness,  by  which  the  acid  is  expelled.     It 
much  resembles  baryta,  seeming  to  sustain  much  the  same  rela- 
tion to 'it  that  soda  sustains  to  potash. 


QUESTIONS. — How  is  sulphate  of  baryta  affected  when  heated  with 
charcoal  ?  What  is  it  called  by  mineralogists  ?  For  what  purpose  is  it 
used?  How  is  nitrate  of  baryta  formed?  400.  Give  the  history,  &c., 
of  strontium?  From  what  is  the  name  derived ?  401.  How  is  the  alka- 
line earth,  strontia,  procured?  What  is  said  of  its  relation  to  baryta? 


BINARYCOM  POUNDS    OP    CALCIUM.  331 


Salts  of  Strontia. 

402.  Carbonate  of  Strontia,  SrO,C02,  is  found  native; — it  is  the  stron- 
tianite  of  mineralogists. 

Sulphate  6f  Strontia,  SrO,S03,  is  also  found  native,  and  is  called 
celestine.  Treated  in  the  same  manner  as  described  for  sulphate  of 
baryta  (309),  the  other  salts  of  strontia  may  be  prepared  from  it. 

Nitrate  of  Strontia,  SrO,N05,  is  prepared  by  dissolving  the  native  cdr- 
bonate  in  diluted  nitric  acid,  or  from  the  sulphide,  as  described  under 
sulphate  of  barjrta.  It  is  much  employed  in  fire-works,  to  give  a  beau- 
tiful red  color  to  the  flame.  To  show  this  red  fire,  mix  intimately  40 
parts  of  this  salt,  13  of  sulphur,  5  of  chlorate  of  potash,  and  4  of  sul- 
phide of  antimony,  and  burn  the  mixture  upon  a  dry  brick,  or  marble 
slab,  in  a  dark  room.  The  nitrate  contains  water,  and  should  be  well 
dried  before  mixing  with  the  other  ingredients.  All  the  compounds  of 
strontia  communicate  a  red  tint  to  flame  in  which  they  are  heated. 


CALCIUM. 
Symbol,  Ca ;  Equivalent,  20 ;  Density,  —  ? 

403.  History,  Etc. — Calcium  is  the  metallic  base  of  lime,  from 
which  it  has  been  obtained,  but  only  in  very  small  quantity.     The 
process  is  precisely  the  same  as  that  given  above  for  obtaining 
barium  from  baryta.     It  is  said  to  be  of  a  brilliant  white  color, 
and  rapidly  oxydizes  in  the  air.     Little  is  known  of  its  other 
properties. 

Binary  Compounds  of  Calcium. 

404,  Protoxide  of  Calcium— Lime,  .CaO;  eq.,  (20  +  8  =)  28. 

—  This  compound, -commonly  known  by  the  name  of  lime  and 
quicklime,  is  obtained  by  exposing  carbonate  of  lime  to  a  strong 

QUESTIONS. — 402.  What  is  the  mineralogical  name  for  carbonate  of 
strontia  ?  Sulphate  of  strontia  ?  How  is  nitrate  of  strontia  prepared  ? 
What  use  is  made  of  it?  403.  Give  the  history,  &c.,  of  calcium.  404.  What 
is  the  common  name  for  protoxide  of  calcium  ?  How  is  it  prepared  from 
the  native  carbonate  ? 


332 


BINARY    COMPOUNDS    OF    CALCIUM. 


red  heat,  so  as  to  expel  its  carbonic  acid.  If  lime  of  great  purity 
is  required,  it  should  be  prepared  from  pure  carbonate  of  lime, 
such  as  Iceland  spar,  or  Carrara  marble ;  but  to  obtain  lime  for 
ordinary  purposes,  common  limestone  is  used. 

The  calcination  of  the  carbonate, 
to  procure  lime  for  common  purposes, 
is  effected  in  kilns,  or  pits,  which  are 
usually  constructed  of  stone,  upon  a 
hill-side,  so  that  the  limestone  may  be 
conveniently  introduced  at  the  top, 
and  the  lime,  after  calcination,  re- 
moved from  the  opening  at  the  bot- 
tom. Wood  is  very  generally  used 
for  the  fuel,  but  bituminous  coal  may 
be  substituted  for  it,  the  pieces  of 
limestone  being  placed  so  that  the 
flames  pass  through  it.  When  the 
calcination  is  finished,  of  which  the 
experienced  eye  can  easily  judge,  the  fire  is  extinguished,  and 
the  lime,  when  cold,  removed.  The  calcination  of  a  large  kiln 
usually  require  five  or  six  days. 

Sometimes  the  calcination  is  carried  on  in  perpetual  kilns,  as 
they-are  called.  The  limestone  is  then  introduced  in  successive 
layers,  with  layers  of  coal  between  them ;  and  the  fire,  once  kin- 
dled, is  continued  for  an  indefinite  time,  layer  after  layer  of  the 
coal  being  consumed,  and  the  lime,  after  calcination,  being 
removed  from  below.  As  the  mass  settles  down  in  the  kiln, 
new  layers  of  limestone  and  coal  are  introduced  at  the  top. 

Lime  is  a  brittle,  white,  earthy  solid,  the  specific  gravity  of 
which  is  about  2*3.  It  phosphoresces  powerfully  when  heated  to 
full  redness,  and  hence  its  use  in  the  Drummond  light  (201).  It 
is  one  of  the  most  infusible  bodies  known ;  fusing  with  difficulty 
even  by  the  heat  of  the  oxyhydrogen  blowpipe. 

Exposed  to  the  air,  it  gradually  absorbs  carbonic  acid,  and 
crumbles  to  powder.  It  has  also  a  powerful  amnit'y  for  water, 


Lime  Kiln. 


QUESTIONS. — How  is  the  calcination  usually  effected?  Describe  the 
mode  of  calcining  lime  by  the  use  of  coal  for  fuel.  Describe  the  pro- 
perties of  lime. 


SALTS    OF    LIME.  333 

which  is  absorbed  instantly  on  boing  poured  upon  it ;  and  tho 
combination  is  attended  with  great  increase  of  temperature,  and 
formation  of  a  white  bulky  hydrate.  The  process  of  slaking  lime 
consists  in  forming  this  hydrate,  and  the  hydrate  itself  is  called 
slaked  lime.  It  differs  from  the  hydrates  of  strontia  and  baryta, 
in  parting  with  its  water  at  a  red  heat.  Recently-slaked  lirno 
dissolves  sparingly  in  water,  and  has  this  singular  property,  that 
it  is  more  soluble  in  cold  than  in  hot  water.  The  solution  has  a 
caustic,  acrid  taste,  and  acts  upon  vegetable  colors  like  the  alka- 
lies.  Exposed  to  the  air,  it  absorbs  carbonic  acid ;  and  if  agi- 
tated, becomes  milky,  from  the  formation  of  insoluble  carbonate 
of  lime. 

Mortar,  for  building,  is  prepared  by  mixing  sand  with  recently- 
slaked  lime.  It  becomes  very  hard  by  exposure  to  the  air,  in 
consequence  of  the  absorption  of  carbonic  acid  by  the  lime. 
Combination  seems  also  to  take  place,  to  some  extent,  between 
the  silica  of  the  sand  and  the  lime.  When  the  limestone  from 
which  the  lime  is  made  contains  a  considerable  portion  of  silica, 
alumina,  &c.,  it  constitutes  hydraulic  cementj  or  water-lime. 
Mortar  prepared  from  this,  has  the  property  of  becoming  hard 
under  water,  which  is  not  the  case  with  that  prepared  from 
pure  lime. 

405.  Chloride  of  Calcium,  CaCl. — This  compound  is  formed  by  dis- 
solving carbonate  of  lime  in  hydrochloric  acid.  It  is  much  used  in  the 
operations  of  the  laboratory,  especially  for  removing  moisture  from 
gases,  which  it  effects  readily  in  consequence  of  its  great  affinity  for 
water.  It  is  often  called  muriate  of  lime. 

Fluoride  of  Calcium,  CaF,  is  the  fluor  spar,  or  Derbyshire  spar  of  mine- 
ralogists. It  is  of  great  use  to  the  chemist  as  affording  the  chief  source 
of  the  element  fluorine. 

I 

Salts  of  Lime. 

406.  Carbonate  of  Lime,  CaO,C02. — This  is  one  of  the  most 
abundant  mineral  productions  known  ;  it  is  found  in  every  country 

QUESTIONS. — In  what  consists  the  slaking  of  lime  ?  Is  lime  soluble  in 
water2  How  is  mortar  prepared  ?  What  is  hydraulic  cement,  or  water- 
lime  ?  405.  How  is  chloride  of  calcium  prepared  ?  What  use  is  made 
of  it  ?  406.  What  varieties  of  carbonate  of  lime  are  mentioned  ? 


334  SALTS    OF    LIME. 

as  limestone,  chalk,  Iceland  spar,  marble,  &c.     It  is  decomposed 
by  heat,  and  furnishes  the  quicklime  used  in  preparing  mortar. 

The  beautiful  stalactites,  frequently  seen  suspended  from  the 
roofs  of  caverns,  are  formed  of  this  compound.  Though  insoluble 
in  pure  water,  it  is  slightly  soluble  in  water  containing  an  excess 
of  carbonic  acid.  Water  permeating  the  soil  above  the  caverns, 
first  becomes  charged  with  carbonic  acid,  and  afterwards  takes  up 
a  little  carbonate  of  lime,  which  is  again  deposited  as  the  water, 
4  drop  after  drop,  hangs  suspended  for  a  time  from  the  roof.  This 
is  occasioned  partly  from  the  evaporation  of  the  water,  and  partly 
by  the  escape  of  the  carbonic  acid,  when  the  water  becomes 
exposed  to  the  free  air  of  the  cavern.  As  a  portion  of  the  water 
falls  to  the  bottom  of  the  cavern,  corresponding  deposits  of  car- 
bonate of  lime,  called  stalagmites,  are  formed  upon  the  floor,  and 
gradually  build  themselves  upward.  Sometimes  a  stalactite  from 
the  roof  is  formed  downward  until  it  reaches  the  corresponding 
stalagmite  from  below,  when  the  two,  becoming  connected,  form 


Stalactites. 

a  column  or  pillar,  as  shown  at  the  left  in  the  figure,  which  is 
from  Knapp's  Chemical  Technology. 

407,  Sulphate  of  Lime,  CaO,S03  +  2HO.— Th'is  compound  is 
well  known  as  gypsum,  and  plaster  of  Paris.  Pure,  crystalized 

QUESTIONS. — How  are  stalactites  in  caverns  formed?  What  are  the 
corresponding  deposits  on  the  floor  of  the  cavern  called?  407.  What 
varieties  of  sulphate  of  lime  are  mentioned  ? 


SALTS    OF    LIME  335 

specimens  are  sometimes  called  sehnite,  and  compact  varieties, 
alabaster.  Common  gypsum  contains  considerable  water,  which 
may  be  expelled  by  heat;  but  there  is  a  variety  destitute  of  water, 
called  anhydrite  by  mineralogists.  When  powdered  gypsum,  the 
water  of  which  has  been  expelled  by  a  moderate  heat,  is  again 
made  into  a  paste  with  water,  it  soon  becomes  hard,  or  "  sets," 
as  the  workmen  say ; — a  property  which  adapts  it  admirably  for 
many  purposes  in  the  arts.  In  stereotyping,  a  coat  of  this  paste  is 
spread  carefully  over  a  page  of  type,  set  in  the  ordinary  manner, 
which,  soon  becoming  hard,  is  removed,  and  a  cast  in  common  type- 
metal  taken  from  it.  This,  after  certain  preparations,  and  the 
emendation  of  any  broken  letters  that  may  be  found,  constitutes 
a-  stereotype  plate,  used  in  printing. 

In  a  very  similar  manner  it  is  used  for  preparing  busts  of  living  per- 
sons. The  process  is  conducted  as  follows  :  The  individual  is  prepared 
by  removing  the  clothing  from  his 
neck  and  shoulders,  coating  the 
hair  with  paste,  and  applying  a 
little  oil  or  soap  to  the  part  which 
is  to  be  covered  by  the  plaster.  He 
then  places  himself  on  his  back  on 
a  table,  his  head  being  supported 
about  an  inch  above  the  table  by  a 
small  block  of  wood,  and  surrounded 
on  three  sides  by  a  box  prepared  for 
the  purpose,  as  represented  in  the 
figure.  The  operator,  having  his 
calcined  plaster  properly  mixed  with 
water,  pours  a  portion  of  it  into  the 
box,  so  that  it  may  fill  up  the  space 
under  the  head ;  and  continues  to 
mix  small  portions  at  a  time,  and 
add  it  to  the  mass,  until  the  whole  tlon  of  Busts' 

head  and  face  are  inclosed,  except  a  small  opening  at  the  nostrils.  The 
whole  soon  becomes  hard,  attended  by  a  considerable  elevation  of  tem- 
perature, but  not  so  much  as  to  be  uncomfortable  to  the  subject  of  the 
operation. . 

In  order  to  remove  this  plaster  inclosure,  the  operator  has  taken  the 
precaution,  before  applying  the  plaster,  to  draw  around  the  head  two 
pieces  of  thread  or  twine,  one  so  that  it  shall  come  just  below  the  ears, 
as  the  person  lies  upon  the  table,  and  the  other  just  above  them,  bring- 
ing the  ends  of  both  around  under  the  chin ;  and  just  as  the  plaster  is 
about  to  set,  taking  one  of  these  threads  by  the  two  ends,  he  pulls  it  out 
laterally  so  as  to  divide  the  mass  into  two  parts,  as  if  cut  with  a  knife. 

QUESTIONS. — What  is  the  effect  when  powdered  gypsum  is  exposed  to  a 
moderate  heat  ?  What  now  is  the  effect  when  it  is  mixed  with  water  ? 
Describe  the  mode  of  forming  plaster  busts  of  living  persons. 


336  -SALTS    OF    LIME. 

When  the  second  thread  has  been  drawn  out  in  this  way,  the  plaster 
inclosure  of  the  face  and  head  will  of  course  be  divided  into  three  parts, 
the  upper  part  covering  the  face,  and  beneath  this  a  ring  covering  the 
ears,  and  below  this  the  third  part  covering  the  back  of  the  head  and 
neck.  The  part  covering  the  face  is  now  to  be  carefully  removed,  which 
may  be  done  without  difficulty ;  but  the  second  piece  which  incloses  the 
ears,  will  have  to  be  divided  below  the  chin  and  at  the  top  of  the  head, 
and  removed  in  two  pieces.  This  being  done,  the  subject  of  the  opera- 
tion is  again  at  liberty  to  remove  himself  from  the  table,  leaving  the 
remaining  piece  in  its  place. 

The  four  pieces  being  brought  together,  each  in  its  proper  place,  it  is 
evident  that  the  operator  has  a  perfect  model  or  mould  of  the  head  and 
•All  the  features  of  the  face,  from  which  the  bust  is  to  be  prepared ;  but  a 
further  description  of  this  part  of  the  process  will  not  be  needed. 

If  a  part  of  the  breast  is  to  be  included  with  the  bust,  the  arrangements 
must  of  course  be  made  accordingly,  in  preparing  the  mould.  The  opera- 
tion requires  some  labor,  but  is  less  disagreeable  to  the  subject  than  might 
be  supposed  before  making  the  trial. 

Sulphate  of  lime  is  extensively  used  as  a  manure  in  many 
countries,  with  excellent  effect.  It  is  slightly  soluble  in  water, 
and  is  often  found  in  well  and  spring  water,  and  gives  it  the 
property  called  hardness. 

Phosphates  of  Lime. — There  are  several  of  these  salts.     One  variety  is 

•  found  native,  and  is  called  'apatite;  it  is  an  essential  ingredient  of  all 

fertile  soils,  and  is  contained  in  all  varieties  of  grain  used  for  bread.     It 

also  constitutes  the  chief  part  of  the  solid  matter  of  the  bones  of  animals. 

408,  Hypochlorite  of  Lime,  CaO,C10.— This  is  the  well-known 
chloride  of  lime,  bleaching '-powder ',  or  bleaching-salt  of  commerce. 
It  is  formed  by  passing  a  current  of  chlorine  through  recently- 
slaked  lime.  It  is  a  white  powder,  and  emits  -a  faint  odor  of 
chlorine.  Great  use  is  made  of  it  in  bleaching  (229).  For  this 
purpose  it  is  dissolved  in  water,  and  the  articles  to  be  bleached 
soaked  in  the  solution,  and  then  dipped  in  very  dilute  acid.  The 
chlorine  which  is  thus  liberated  produces  the  bleaching  effect. 
The  process  is  usually  several  times  repeated:  It  is  also  used  as 
a  disinfecting  agent,  the  chlorine,  as  it  is  gradually  liberated, 
having  the  property  of  destroying  deleterious  gases  present  in  the 
r  atmosphere. 

The  commercial  value  of  bleaching-salt  depends  entirely  upon  the 
quantity  of  chlorine  it  is  capable  of  evolving  when  used,  and  is  usually 
determined  by  the  quantity  of  indigo  a  given  weight  of  it  will  bleach. 

QUESTIONS. — What  is  said  of  the  phosphates  of  lime  ?  408.  What  is 
hypochlorite  of  lime  ?  What  use  is  made  of  it  ? 


BINARY     COMPOUNDS     OF     MAGNESIUM.        837 

Tests  of  Lime. — The  proper  test  for  lime  is  oxalic  acid,  which 
forms  with  it,  in  solution,  an  insoluble  white  precipitate.  Oxalate 
of  ammonia  is  generally  used.  A  salt  of  lime  dissolved  in  alcohol 
gives  to  the  flame  a  red  color,  very  similar  to  that  communicated 
by  strontia  (402),  but  of  a  slightly  different  tint. 


MAGNESIUM. 
Symbol,  Mg;  Equivalent,  12;  Density,  1-87 

409.  History,  Etc. — Magnesium  is  obtained  from  its  chloride 
by  passing  vapor  of  sodium  or  potassium  over  it  when  heated  to 
redness  in  a  glass  tube;  the  alkaline  chloride  formed,  and  any 
undecomposed  chloride  of  magnesium  which  may  remain,  are 
washed  out  with  cold  water,  and  the  metallic  magnesium  subsides. 

It  is  a  white  metal,  of  considerable  brilliancy,  and  quite  malle- 
able. Heated  in  the  open  air,  it  readily  takes  fire,  and  burns 
with  a  brilliant  flame,  producing  the  protoxide  of  the  metal.  It 
is  rapidly  oxydized  by  boiling,  but  not  by  cold  water. 


Binary  Compounds  of  Magnesium. 

410.  Protoxide  of  Magnesium— Magnesia,  MgO. — Magnesia 
is  best  obtained  by  heating  the  carbonate  to  redness,  by  which  the 
carbonic  acid  is  expelled.  It  may  also  be  prepared  by  decom- 
posing nitrate  of  magnesia  by  heat.  It  is  a  soft,  white  powder, 
and  is  usually  sold  under  the  name  of  calcined  magnesia.  It  is 
very  slightly  soluble  in  water,  requiring  for  this  purpose  5000 
or  6000  times  its  own  weight  of  water.  Hydrate  of  magnesia, 
MgO, HO,  is  found  native  at  Hoboken,  New  Jersey,  and  other 
places.  Magnesia  is  very  infusible,  and  communicates  this  pro- 
perty to  minerals  in  which  it  predominates,  as  talc  and  soapstone. 

Magnesia  is  extensively  used  in  medicine  as  an  antiacid.     In 

QUESTIONS. — What  tests  of  lime  are  mentioned  ?     409.  How  is  magne- 
sium obtained  ?     What  is  said  of  the  metal  ?     410.  Describe  the  protoxide 
of  magnesium.     What  use  is  made  of  magnesia  ? 
29 


838  SALTS    OF    MAGNESIA. 

the  state  of  hydrate  it  is  said  to  be  a  good  remedy  in  cases  of 
poisoning  with  arsenic. 

Chloride  of  Magnesium,  MgCl. — Chloride  of  magnesium,  which,  as  we 
Lave  just  seen,  is  made  use  of  to  obtain  the  metal,  is  best  procured  by 
dissolving  magnesia,  in  hydrochloric .  acid,  and  adding  to  the  solution  an 
excess  of  sal-ammoniac ;  and,  after  expelling  the  water,  heating  the 
residue  in  a  platinum  crucible,  by  which  means  the  sal-ammoniac  used 
will  be  driven  ofi".  ^Without  the  sal-ammoniac,  the  chloride  of  magne- 
sium would  be  decomposed  by  the  heat  required  to  expel  the  water. 


Salts  of  Magnesia. 

411.  Carbonate  of  Magnesia,  MgO,C02.— Carbonate  of  mag- 
nesia is  found  native,  in  the  maynesite  of  mineralogists,  and  may 
also  be  formed  from  the  native  sulphate  by  precipitation  with  an 
alkaline  carbonate.  It  is  nearly  insoluble  in  pure  water,  but  dis- 
solves in  water  impregnated  with  carbonic  acid,  forming  the  liquid 
magnesia  of  the  shops.  When  obtained  by  precipitation  with  an 
alkaline  carbonate,  it  always  contains  a  portion  of  hydrate  of  mag- 
nesia, and  is  usually  seen  in  beautiful  square  blocks,  which  are 
remarkable  for  their  lightness. 

It  is  extensively  used  in  the  practice  of  medicine. 

Sulphate  of  Magnesia,  MgO,S03. — This  is  the  well-known 
Epsom  salt,  used  in  medicine.  It  is  not  unfrequently  found  in 
the  waters  of  mineral  springs,  as  at  Epsom,  in  England,  and  may 
readily  be  formed  by  dissolving  magnesia,  or  its  carbonate,  in 
sulphuric  acid,  and  by  the  action  of  this  acid  upon  the  mineral 
called  dolomite,  which  is  a  double  carbonate  of  magnesia  and 
lime.  Its  crystals  contain  7  eq.  of  water  of  crystalization. 

It  is  very  soluble,  and  has  a  bitter,  saline  taste.  It  may  readily 
be  distinguished  from  sulphate  of  soda  by  the  form  of  its  crystals, 
or  by  pouring  into  a  solution  of  it  some  caustic  potassa,  which  will 
cause  a  white  precipitate.  In  sulphate  of  soda,  no  precipitate  will 
be  formed. 

QUESTIONS. — Describe  the  mode  of  preparing  chloride  of  magnesium. 
411.  Describe  the  carbonate  of  magnesia.  What  is.  the  common  name 
of  sulphate  of  magnesia  ?  Where  is  it  sometimes  found  ?  How  may  it 
be  distinguished  from  sulphate  of  soda  ? 


ALUMINUM.  339 

Silicates  of  Magnesia,  of  which  there  are  several,  abound  in  nature, 
especially  in  the  talcose  and  serpentine  rocks. 

There  is  no  specific  test  of  magnesia,  but  it  is  distinguished  from  other 
substances  by  different  tests ;  and  from  most  of  its  soluble  salts  phosphate 
of  soda,  with  ammonia,  separates  a  white  precipitate,  which  is  a  double 
phosphate  of  magnesia  and  ammonia. 


The  oxides  of  these  metals,  which  constitute  the  earths,  are 
called  alumina,  glucina,  zirconia,  thorina,  yttria,  &c.  They 
are  distinguished  from  both  the  alkalies  and  alkaline  earths 
by  being  quite  insoluble  in  water,  and,  of  course,  destitute 
of  any  alkaline  reaction.  They,  however,  combine  readily 
with,  and  neutralize  the  most  powerful  acids. 


GROUP  III. 
ALUMINUM 

ULUCINUM  Metals,  the  protoxides  or  sesquioxides  of  which  are  earths.— 

ZIRCONIUM 

THORIUM 

YTTRIUM 

ERBIUM 

TERBIUM 

CERIUM 

LANTHANUM 

DIDYMIUM 

ALUMINUM. 

• 

Symbol,  Al;  Equivalent,  13-7;  Density,  3-7. 

412.  History,  Etc. — The  metal  aluminum  is  obtained  by  de 
composing  chloride  of  aluminum  by  the  action  of  sodium  or 
potassium,  in  the  same  manner  as  magnesium  is  prepared  from 
its  chloride.  It  is  found,  after  the  process,  in  small  globules, 
which  may  be  brought  into  a  single  mass  by  melting  it  in  a  close 
crucible,  or  under  dry  chloride  of  sodium.  Instead  of  chloride 
of  aluminum,  the  mineral  called  cryolite,  which  is  a  double 
fluoride  of  aluminum  and  sodium,  may  be  us*ed  in  its  preparation. 

Aluminum  is  very  malleable,  and  has  the  brilliant  lustre  and 
white  color  of  silver.  It  is  not  oxydized  in  the  atmosphere  at 
ordinary  temperatures,  but  burns  brilliantly  when  heated  to  red- 
ness. Cold  water  does  not  affect  it.  A  small  piece  that  had 
been  rolled  was  found  to  have  a  density  of  3-7,  as  given  above. 

The  name  of  this  metal,  aluminum,  is  derived  from  alum,  a  double  sul- 
phate of  alumina  and  potassa,  from  which  the  earth  is  very  readily 
obtained. 

QUESTIONS. — What  metals  belong  to  Group  III.  ?  How  are  they  cha- 
racterized ?  412.  How  is  metallic  aluminum  prepared  ?  What  native 
mineral  may  be  used  for  the  purpose,  instead  of  the  chloride  ?  Describe 
the  metal. 


4 

340          BINARY     COMPOUNDS    OF    ALUMINUM. 

Binary  Compounds  of  Aluminum. 

413.  Sesquioxide  of  Aluminum,  A1203.  —  This  is  the  earth 
alumina,  and  is  one  of  the  most  abundant  of  nature's  pro- 
ductions. Like  silica,  it  is  found  in  every  soil,  and  in  almost 
all  rocks  upon  the  face  of  the  earth.  Crystalized,  it  forms  the 
ruby  and  the  sapphire,  two  of  the  most  valuable  gerns.  Emery, 
also,  so  much  used  in  the  arts,  is  chiefly  composed  of  this  earth. 
It  forms  a  large  part  of  clay,  and  gives  to  it  its  tenacious  character, 
fitting  it  for  the  use  of  the  potter. 

Pure  alumina  is  a  white  powder,  without  taste  or  smell.  It  is 
easily  prepared  by  pouring  solution  of  caustic  potash  into  a  solu- 
tion of  alum,  and  washing  and  heating  the  soft  mass  that  is 
precipitated.  It  contracts  much  in  drying,  and  the  dried  mass 
adheres  tenaciously  to  the  tongue  when  applied  to  it. 

Alumina,  though  usually  serving  as  a  base  in  the  compounds 
tehfch  it  forms,  occasionally  becomes  the  electro-negative  ele- 
melit,  and  serves  the  part  of  an  acid.  Thus,  it  combines  with 
potassa  to  form  aluminate  of  potassa,  and  with  baryta  in  like 
manner.  The  mineral  called  spinelle  is  a  native  aluminate  of 
magnesia. 

This  earth  is  remarkable  for  its  tendency  to'  unite  with  organic 
substances.  If  a  cotton  cloth  is  immersed  in  a  solution  of  acetate 
of  alumina,  the  earth  will  deposit  itself  completely  on  the  fibres 
of  the  cotton  and  leave  the  acetic  acid  free.  On  this  principle 
depend  some  of  the  most  important  processes  in  calico-printing. 

When  heated  with  nitrate  of  cobalt,  it  forms  a  beautiful  blue  com- 
pound. 

Native  hydrate  cf  alumina  is  occasionally  found,  as  gibbsite  and 
diaspore. 

Chloride  of  Aluminum,  A12C13. — This  compound  is  interesting  as  fur- 
nishing the  means  of  obtaining  the  metal  aluminum.  For  this  purpose 
it  must  be  anhydrous,  and  is  obtained  by  passing  a  current  of  dry 
chlorine  through  a  mixture  of  alumina  and  charcoal,  heated  to  redness, 
in  a  porcelain  tube. 

QUESTIONS. — 413.  What  is  said  of  the  abundance  of  alumina?  What 
gems  are  mentioned  as  composed  of  this  earth  ?  Describe  alumina. 
Does  it,  in  combination,  act  as  a  base  or  an  acid  ?  What  is  said  of  its 
tendency  to  unite  with  organic  substances  ?  How  is  chloride  of  aluminum 
formed? 


SALTS    OP    ALUMINA.  341 


Salts  of  Alumina. 

414.  Sulphate  of  Alumina,  A1203,3S03.  — This  salt,  though 
containing  3  eq.  of  acid,  is  considered  a  neutral  (349)  sulphate. 
It  is  obtained  by  treating  the  purest  clays  with  sulphuric  acid, 
moderately  diluted.     It  is  very  soluble  in  water,   and  may  be 
obtained  in  small  crystals,  which  contain  18  eq.  of  water.     It  is 
used  in  dyeing. 

415.  Sulphate  of  Alumina  and  Potash,  A1203,3S03  +  KO,S03. 
— This  double  salt  is  the  well-known  alum  of  commerce.     It  is 
usually  formed  from  a  mineral  substance  called  alum-slate,  which 
is  an  argillaceous,  slaty  rock,  containing  iron  pyrites.     It  is  some- 
times found  naturally  formed  as  an  efflorescence  upon  the  surface 
of  the  rock. 

Alum  is  usually  seen  crystalized  in  octahedrons,  which  always 
contain  24  eq.  of  water;  it  is  very  soluble  in  boiling  water,  and 
has  a  sweetish,  astringent  taste.  When  the  crystals  are  heated, 
they  melt  and  froth  up  very  much,  in  consequence  of  the  large 
quantity  of  water  they  contain.  Alum  is  much  used  in  medicine 
and  in  the  arts,  especially  in  dyeing  and  calico-printing. 

The  alumen  ustum,  or  burnt  alum,  used  in  medicine  as  a  caustic, 
is  alum  that  has  been  deprived  of  its  water  of  crystalization  by 
heat. 

Common  or  potash  alum  is  the  type  of  a  whole  family  of  alums ; 
as  soda  alum,  ammonia  alum}  iron  alum,  chromium  alum}  &c. 
Soda  and  ammonia  alums  are  produced  by  causing  these  sub- 
stances to  replace  the  potash  in  common  alum ;  and  iron  and 
chromium  alums,  by  replacing  the  alumina  by  the  ses^uioxides 
of  iron  and  chromium.  These  alums  are  all  exceedingly  alike  in 
their  various  properties,  and  all  contain,  when  crystalized,  24 
atoms  of  water. 

The  relation  of  these  different  alums  (183)  to  each  other  in 
composition  will  best  be  seen  by  comparing  their  formulae. 

QUESTIONS. — 414.  How  is  sulphate  of  alumina  formed?     415.  What  is 
the  composition  of  alum  ?     From  what  is  it  usually  formed  ?     What  use 
is  made  of  it  ?     What  are  some  of  the  different  alums  that  are  known  f 
20*  * 


342  SALTS    OF    ALUMINA. 


{1,  Potash,  or  common  alum KO,S03  4.  Alt03,3S03  -j-  24HO. 
2.  Soda  alum NaO,S03  4-  A1203,3S03  4-  24HO. 
3.  Ammonia  alum NH40,S03  -f  A1203,3S03  -f  24HO 


III.  7    Manganeso-potash  alum....;.,  KO,S03  -j-  Mn203,3S03  -f-  24HO. 

IV.  8.  Chromio-potash  alum KO,S03  -f  Cr203,3S03  -j-  24HO. 

•»  . 

Both  the  manganese  and  chromo  series  have  a  soda  and  an  ammonip 
alum,  the  same  as  the  other  series. 

Cubic  alum,  so  called  because  its  crystals  usually  are  cubes,  is 
formed  by  pouring  solution  of  carbonate  of  potassa  into  a  saturated 
solution  of  common  alum  at  about  122°,  constantly  stirring  the  mix- 
ture for  some  time.  Its  composition  is  KO,S03+ A12032SO  +  9HO. 

416.  Silicates  of  Alumina, — Several  double  silicates  of  alumina 
and  other  bases  are  found  native,  some  of  which  are  of  great  im- 
portance in  the  arts.  Feldspar  is  a  double  silicate  of  alumina 
and  potash,  while  albite,  or  Cleavelandite,  is  a  double  silicate 
of  alumina  and  soda.  Spodutneme  and  petalite  are  the  same  as 
the  latter,  except  that  they  contain  less  soda,  and  a  small  portion 
of  lithia. 

Sometimes  feldspar  undergoes  a  natural  decomposition,  losing 
its  potash  and  part  of  its  silica,  and  is  then  called  kaolin.  This 
substance,  which  is  essentially  silicate  of  alumina,  more  or  less 
pure,  is  the  basis  of  all  the  varieties  of  porcelain  or  China-ware. 
The  articles  are  made  of  this  of  the  proper  form,  and,  when  dry, 
are  exposed  to  a  high  temperature  in  a  furnace,  by  which  they 
become  very  compact,  but  do  not  fuse.  They  are  then  dipped  in 
the  glaze,  which  consists  chiefly  of  feldspar,  ground  to  a  fine  pow- 
der, and  suspended  in  water,  a  coating  of  which  adheres  over  the 
surface;  and  when  the  articles  are  dried  and  again  subjected  to 
the  heat  of  the  furnace,  it,  fuses  and  forms  a  glassy  envelope, 
which  incorporates  itself  with  the  body  previously  formed,  and 
increases  its  compactness  and  strength.  The  glaze  also  renders 

QUESTIONS. — Of  those  alums  mentioned  in  the  table,  what  is  the  dif- 
ference in  composition  between  the  first  and  second?  The  first  and 
third  ?  The  first  and  fourth  ?  First  and  seventh  ?  Seventh  and  eighth  ? 
416.  What  native  silicates  of  alumina  are  mentioned  ?  What  is  kaolin  ? 
What  use  is  made  of  it  ?  Describe  the  mode  of  manufacturing  articles 
of  porcelain.  " 


SALTS    OF    ALUMINA.  343 

\jhem  impervious  to  liquids,  and  even  to  the  gases.  1^  the  finer 
kinds  of  porcelain,  the  kaolin.,  which  constitutes  the  body,  is 
mixed  with  some  substance,  as  alkali  or  lime,  by  which  it  is  ren- 
dered partially  fusible,  and  the  glaze  therefore  becomes  more 
perfectly  incorporated  with  it,  so  as  to  render  articles  made 
of  it  slightly  translucent.  The  colors  are  applied  after  the  first 
burning,  and  before  the  glaze,  and  are  composed  entirely  of 
metallic  oxides. 

417.  All  the  different  kinds  of  clay  are  composed  essentially 
of  alumina  and  silica,  both  of  which  are  very  infusible,  except 
when  mixed  with  the  alkalies  or  lime,  or  certain  metallic  oxides, 
especially  the  oxides  of  iron.  Common  clay  always  contains  car- 
bonate of  lime  and  oxide  of  iron,  and  is  therefore  quite  fusible. 
Fire  day,  so  called  because  of  its  infusibility,  contains  no  lime; 
when  free  from  metallic  oxides  it  is  called  pipe  clay,  and  articles 
made  of  it  are  uncolored  when  removed  from  the  fire. 

Stone-ware  is  made  of  an  infusible  clay;  and  when  the  articles 
are  sufficiently  heated  in  the  furnace,  common  salt  is  thrown  upon 
them,  the  soda  of  which,  combining  with  the  materials  of  the 
clay,  forms  a  fusible  compound  that  constitutes  the  glaze.  With- 
out this  the  articles  would  be  porous,  and  water  and  other  liquids 
would  percolate  through  them. 

Red  earthen-ware  is  made  of  the  most  common  kinds  of  clay, 
which  contain  lime  and  iron,  and  is  so  fusible,  that  only  a  mode- 
rate heat  is  needed  in  baking  articles  made  of  it.  The  articles, 
after  being  shaped  upon  the  potters'  wheel,  are  thoroughly  dried, 
and  then  coated  over  with  litharge  (oxide  of  lead),  in  fine  powder, 
which,  by  the  heat  of  the  furnace  afterwards  applied,  fuses  arid 
spreads  over  the  surface  so  as  to  form  a  fine  glaze.  Such  vessels, 
however,  should  never  be  used  with  acids,  which  Would  attack 
the  oxide  of  lead  and  produce  poisonous  compounds. 

"Bricks  are  usually  made  of  the  same  kind  of  clay  as  that  just 
described.  No  glaze  is  required  for  them.  The  best  bricks  are 
now  pressed  when  partially  dry,  to  render  them  more  solid,  and 

QUESTIONS. — 417.  Of  what  are  all  the  different  kinds  of  clay  com- 
posed ?  What  is  fire  clay  ?  How  is  the  glaze  applied  to  articles  of  stone- 
ware ?  Describe  red  earthen-ware.  How  are  bricks  made  ? 


344     GLUCINUM,     ZIRCONIUM,    AND    THORIUM. 

to  give  them  a  smoother  surface.  The  red  color  is  occasioned  by 
the  oxide  of  iron  in  the  clay,  or  the  sand  mixed  with  it,  which, 
by  the  heat  in  burning,  becomes  peroxidized. 

418.  Glucinum,  G;  Eq.,  4-7. — This  metal  receives  its  name  from  the 
circumstance  that  the  salts  of  its  oxide,  glucina,  are  sweet  (Greek,  ylukus, 
sweet,)  to  the  taste.     It  is  obtained  from  its  chloride  in  the  same  manner 
a;  magnesium  and  aluminum. 

Glucina  is  an  oxide  of  the  metal,  but  whether  it  is  a  protoxide,  GO, 
or  a  sesquioxide,  G209,  has  not  been  determined.  It  is  obtained  chieily 
from  the  mineral  species  called  beryl,  and  therefore  the  metal  has  by 
some  been  called  beryllum.  If  we  consider  it  as  a  sesquioxide,  the  equiva- 
lent of  the  metal  will  be  6-96,  instead  of  the  mirnber  given  above. 

419.  Zirconium,  Zr ;  Eq.,  84. — Zirconium,  in  combination  with  oxygen, 
is  found  in  the  mineral  species  zircon,  which  is  a  silicate  of  zirconia.     It 
is  present  also,  in  small  quantity,  in  some  few  other  minerals. 

The  earth  zirconia  is  believed  to  be  a  sesquioxide  of  the  metal,  Zr203. 

420.  Thorium,  Th ;  Eq.,  59-6. — Thorium  is  found  only  in  a  few  very  rare 
minerals,  as  thorite,  pyrochlore,  and  monasite. 

The  earth  thorina  is  a  protoxide,  ThO. 

Yttrium,  Erbium,  and  Terbium  are  found  associated  in  a  very  few  rare 
minerals,  especially  in  gadolinile,  a  mineral  species  obtained  chiefly  from 
Sweden. 

Cerium,  Lanthanum,  and  Didymium  occur  together  in  several  mineral 
species,  cerite,  allanite,  orthite,  &c.,  but  are  obtained  only  in  small  quantity. 
Of  these  six  metals  last  mentioned,  little  is  really  known ; — except  yttrium 
and  cerium,  they  have  but  recently  been  discovered. 


GROUP  IV. 
MANGANESE 
IRON 
ZING 

CHROMIUM 
CADMIUM 
TIN 

COBALT 
NICKEL 


Metals  which  decompose  vapor  of  water  at  a  red  heat,  but 
are  not  acted  upon  by  liquid  water. 


421.  The  metals  of  this  group  aire  not  as  well  characterized  as 
those  of  some  of  the  other  groups.  All  that  we  have  named  as 
included  in  it  do  indeed,  at  a  red  heat,  decompose  the  vapor  t>f 

QUESTIONS. — What  occasions  the  red  color  of  bricks  ?  418.  Describe 
glucinum,  and  the  mode  of  preparing  it.  419.  In  what  is  zirconium 
found?  420.  What  other  metals  are  mentioned  as  belonging  to  this 
group  ?  Name  the  metals  of  Group  IV.  How  are  they  characterized  ? 
421.  Are  the  metals  of  this  group  as  well  characterized  as  those  of  some 
other  groups  ? 


MANGANESE.  345 

water,  but  some  of  them  also  act  slightly  upon  liquid  water. 
This  is  the  case  more  particularly  with  the  first  named,  man- 
ganese ;  but  some  of  the  others,  as  iron  and  zinc,  are  oxydized  by 
water,  at  ordinary  temperatures,  especially  if  atmospheric  air  be 
also  present. 

MANGANESE. 
Symbol,  Mn;  Equivalent,  28;  Density,  8 -3. 

422.  History. — Manganese  was  first  obtained  by  Grahn,  from 
the  substance  then  called  magnesia  nigra,  which  has  since  been 
found  to  be  an  oxide  of  this  metal.     It  received  its  present  name 
to  distinguish  it  from  magnesium,  which  has  already  been  de- 
scribed.    It  is  'never  found  in  nature  in  its  metallic  state,  but  its 
compounds  are  very  generally  diffused,  and  traces  of  it  occur  in 
both  animal  and  vegetable  substances. 

423.  Preparation. — Metallic  manganese,  in  consequence  of  its 
great  affinity  for  oxygen,  is  not  obtained  without  considerable  diffi- 
culty.    To  procure  it,  the  black  oxide,  in  fine  powder,  is  mixed 
into  a  paste  with  oil  and  lampblack,  and  exposed,  in  a  close  cru- 
cible, to  the  highest  heat  of  a  powerful  furnace.     The  oxide 
should  first  be  heated  alone  in  a  covered  crucible, 

to  reduce  it  to  the  form  of  protoxide,  and  this 
then  mixed  with  the  lampblack  and  oil,  as  directed 
above.      The  last  heating,  which  should  be  con- 
tinued two  hours,  is  best  performed  in  a  porcelain 
crucible,  well  closed  by  a   cover,  and  then  luted 
in  a  common  Hessian  crucible,  as  shown  in  the 
figure,  which   represents   a    section   through  the     Preparation  of 
centres    of    both    crucibles.      "A   little   powdered      Manganese, 
borax  mixed  with  the  materials  facilitates  the  collection  of  the 
metallic  globules  into  a  mass. 

The  metal  will  be  found  in  a  button  at  the  bottom  of  the 
crucible. 

QUESTIONS. — 422.  Give  "the  history  of  manganese.      323.  How  is  the 
metal  prepared  ? 


346       BINARY     COMPOUNDS    OP    MANGANESE. 

424.  Properties.  —  Manganese  is  a  hard,  brittle  metal,  of  a 
grayish-white   color,   and   granular  texture.      It  is  exceedingly 
infusible,  requiring  the  highest  heat  of  a  wind-furnace  for  fusion. 
It  soon  tarnishes  on  exposure  to  the  air,  and  absorbs  oxygen  with 
rapidity  when  heated  to  redness  in  open  vessels.     In  water  at 
ordinary  temperatures  it  is  slowly  oxydized,  and  the  action  becomes 
more  decided  as  the  heat  is  raised. 

The  metal  is  best  preserved  in  pieces  of  glass  tube,  hermetically 
N  ealed. 

Binary  Compounds  of  Manganese. 

425.  Oxides  of  Manganese, — There  are  six  oxides  of  man- 
ganese, viz. : 

The  protoxide,  MnO,  which  is  a  powerful  base. 

The  sesquioxide,  Mn203,  which  is  a  weak  base. 

The  red  oxide,  Mn304,=MnO  +  Mn203,  a  saline  oxide  (344 :  4). 

The  binoxide,  Mn02,  called  also  peroxide  and  Hack  oxide. 

Manganic  acid,  Mn03,  and 

Permanganic  acid,  Mn207. 

426.  Protoxide  of  Manganese,  MnO. — This  compound,  though  existing 
frequently  in  combination,  is  obtained  in  a  separate  state  with  some 
difficulty,  in  consequence  of  its  strong  tendency  to  absorb  oxygen  from 
the  air.     The  following  is  the  best  method  of  procuring  it.     A  glass  tube 
with  a  bulb,  A,  near  the  middle,  is  provided,  and  the  bulb  partly  filled 


Preparation  of  MnO. 

with  powdered  carbonate  of  manganese.  A  larger  tube,  B,  is  filled 
loosely  with  dry  chloride  of  c&lcium,  or  pieces  of  pumice  stone  impreg- 
nated with  strong  oil  of  vitriol,  and  connected  with  the  first  tube,  as 

QUESTIONS. — 424.  What  are  the  properties  of  manganese?  425.  How 
many  compounds  of  manganese  and  oxygen  are  there  ?  42G.  Describe 
the  mode  of  preparing  the  protoxide  by  means  of  hydrogen  gas. 


BINARY  COMPOUNDS  OP  MANGANESE.    347 

shown  in  the  figure.      The  two-necked  bottle,  C,  contains  pieces  of  zinc 
and  water. 

When  the  whole  is  arranged  as  represented,  some  oil  of  vitriol  is  poured 
into  the  bottle,  C,  and  the  whole  interior  of  the  apparatus  is  soon  filled 
with  hydrogen  gas,  which  is  deprived  of  its  moisture  by  passing  the  tube, 
B,  so  that  dry  hydrogen  only  surrounds  the  manganese  compound.  A 
spirit-lamp  is  now  placed  under  A,  the  heat  of  which  decomposes  the 
carbonate  of  manganese,  leaving  the  protoxide  as  a  fine  powder ;  and  the 
absorption  of  oxygen  is  prevented  by  the  hydrogen. 

After  a  proper  time  the  tube,  A,  may  be  removed,  and  the  extreme 
point  closed  hermetically  by  the  lamp ;  the  tube  on  the  other  side  of  the 
bulb  may  also  be  drawn  out  and  closed 
in  the  same  manner,  which  is  accom- 
plished the  more  readily  if,  after  intro- 
ducing the  manganese  compound,  the 
tube  has  been  a  little,  reduced,  as  Preparation  of  MnO. 

shown  in  the  accompanying  figure. 

Prepared  in  this  way,  the  protoxide  is  a  powder  of  a  delicate  green 
color ;  and  thus  inclosed  from  the  air,  may  of  course  be  preserved  for 
any  length  of  time. 

427.  Peroxide  of  Manganese,  Mn02. — This  is  the  common, 
or  Uach  oxide,  of  this  metal.     It  is  found  in  considerable  abun- 
dance in  the  State  of  Vermont,  and  in  other  places  in  this  country, 
and  in  Europe.     Heated  alone,  it  is  reduced  to  the  sesquioxide, 
Mn203,  but  when  heated  with  sulphuric  acid  it  is  reduced  to  the 
protoxide,  with  which  the  acid  combines.      This  last  operation 
may  be  performed  in  glass  vessels.      Heated  with  hydrochloric 
acid,  chloride  of  manganese  is  formed,  and  chlorine  evolved.     It 
is  much  employed  in  the  arts,  in  the  manufacture  of  glass,  and 
bleaching-salt,  and  for  other  purposes.     When  crystalized,  it  is 
called  by  mineralogists  pyrolusite.     The  sesquioxide  very  much 
resembles  the  peroxide  in  appearance,  and  is  often  fraudulently 
sold  for  it. 

428.  Manganic  Acid,  MnO$. — This  compound  has  never  been  obtained 
in  a  separate  state,  but  only  in  combination  with  bases.     It  is  interesting 
as  the  first  metallic  acid  we  are  called  to  consider  in  the  progress  of  our 
course.      It  is  formed,   in  combination  with  potash,  by  heating  equal 
weights  of  peroxide  of  manganese  and  nitrate  of  potash  to  dull  redness  in 
an  open  crucible.     The  compound,  manganate  of  potash,  is  of  a  dark-green 
color,  and  has  long  been  known  by  the  name  of  chameleon  mineral.     Dis- 
solved in  cold  water,  it  forms  a  beautiful  green  solution,  which  by  con- 
tinued dilution  changes  to  blue,  purple,  and,  finally,  to  a  brilliant  red. 

QUESTIONS. — 427.  Is  the  black,  or  peroxide,  found  native  ?  What  use 
is  made  of  it  ?  428.  Describe  the  mode  of  preparing  manganate  of  potash. 
What  is  it  called? 


348       SALTS  OF  MANGANESE. — IRON. 

Hence  its  name.     The  changes  are  much  more  rapid  when  hot  water 
is  used. 

429.  Permanganic  Acid,  Mn207. — This  acid,  in  combination  with  potash, 
is  formed  when  solution  of  the  manganate  of  potash  is  made  with  hot  water, 
as  above  described,  by  the  absorption  of  oxygen  from  the  air.  It  is  to  the 
formation  of  this  compound  that  the  red  color  is  owing,  which  is  finally 
obtained  by  solution  of  chameleon  mineral. 

From  this  red  solution  purple  crystals  of  permanganate  of  potash  may 
be  obtained;  but  when  an  attempt  is  made  to  separate  either  this  or  the 
preceding  acid  from  the  bases  with  which  they  are  united,  they  are 
decomposed. 

Chloride  of  Manganese  is  formed  by  digesting  the  black  oxide  in  hydro- 
chloric acid.  There  are  two  known,  the  protochloride,  MnCl,  and  sesqui- 
chloride,  MngCl8. 

Salts  of  Manganese. 

There  are  several  salts  of  manganese,  but  the  only  one  of  im- 
portance in  the  arts  is  the  following : 

430,  Sulphate  of  Manganese,  MnO,S03. — This  salt  is  formed 
by  digesting  the  peroxide  in  strong  sulphuric  acid  by  the  aid  of 
heat,  and  filtering  when  it  has  become  cold.     The  crystals  of  the 
salt  are  of  a  rose-red  color,  and  are  very  soluble  in  water.     They 
always  contain  some  water  of  crystalization,  the  quantity  depend- 
ing upon  the  temperature  of  the  solution  in  which  they  are 
formed. 

Carbonate  of  Manganese,  MnO,COr  is  found  na-tive  in  the  mineral 
called  diallogite. 

IRON. 
Symbol,  Fe  (Ftrrum)',  Equivalent,  28;  Density,  7 '7  to  7-9, 

431.  History, — Iron,  the  most  abundant  and  most  useful  of 
all  the   metals,  has   been  known  from   the  remotest  antiquity. 
The  ores  of  the  metal,  as  well  as  the  metal  itself,  and  some  of  its 
manufactures,  are  mentioned  in  the  writings  of  Moses,  and  it  is 
well  known   the  ancient  Greeks  and  Romans  were  acquainted 
with  it. 

Iron  has  been  found  native  in  small  quantities  in  different 

QUESTIONS. — 429.  How  is  permanganate  of  potash  formed  ?  430.  De- 
scribe the  sulphate  of  manganese.  431.  Has  iron  been  long  known?  Has 
it  been  found  native  ? 


IRON.  349 

countries,  but  recently  a  real  mine  of  very  pure  iron  seems  to 
have  been  discovered  in  the  territory  of  Liberia,  on  the  western 
coast  of  Africa. 

The  occurrence  of  iron  of  meteoric  origin,  associated  with 
nickel,  and  sometimes  with  cobalt  and  other  metals,  is  not 
uncommon.  One  mass,  at  least,  of  this  kind  was  actually  seen 
to  fall  from  the  atmosphere,  which  was  subsequently  examined ; 
but  many  others  have  been  found  in  such  situations  as  to  leave 
no  doubt  that  they  originated  in  the  same  manner.  As  no  such 
compound  has  ever  been  found  in  proper  iron-mines,  it  is  believed 
that  these  bodies  must  have  their  origin  in  some  region  foreign 
to  the  earth. 

Common  meteorites,  which  have  often  been  seen  to  fall  from 
the  atmosphere,  are  of  a  different  composition,  containing  usually 
no  metallic  iron,  but  various  compounds  of  iron,  manganese, 
sulphur,  &c. 

There  are  many  ores  of  iron,  but  the  most  important  are  the 
hydrated  peroxide,  called  by  mineralogists  brown  hematite  /  the 
peroxide  (specular  iron,  or  red  hematite),  and  the  black  or  mag- 
netic oxide,  which  is  a  compound  of  the  two  preceding.  The 
last  is  the  natural  magnet,  or  loadstone.  English  iron  is  obtained 
chiefly  from  the  clay-iron  stone,  which  is  an  impure  carbonate  of 
iron,  found  abundantly  in  connection  with  the  coal-meas'ures ; 
but  in  this  country  the  metal  is  extracted  almost  entirely  from 
the  ores  previously  mentioned. 

432.  Preparation. — The  preparation  of  perfectly  pure  iron  is 
a  matter  of  considerable  difficulty ;  but  the  ordinary  method  of 
reducing  it  from  its  ores,  is,  to  heat  them  intensely,  after  having 
been  reduced  to  small  fragments,  with  charcoal  or  coke,  and  lime 
or  siliceous  sand,  as  the  nature  of  the  particular  ore  may  require. 
The  oxygen  of  the  oxide  of  iron  is  absorbed  by  the  heated  carbon 
and  carried  off  as  carbonic  acid,  while  the  flux  — for  so  the  lime 
or  sand  is  called  when  used  for  this  purpose  —  unites  with  the 
earthy  part  of  the  ore  and  forms  a  fusible  compound,  that  remains 

QUESTIONS. — What  is  said  of  meteoric  iron  ?     What  metals  are  usually 
found  in  combination  with  meteoric  iron  ?     What  are  some  of  the  most 
important  ores  of  iron  ?     432.  Describe  the  ordinary  modes  of  reducing 
the  ores  of  iron.     Why  are  fluxes  used  in  the  operation  ? 
30 


350 


IRON. 


upon  the  surface ;  the  melted  iron,  by  its  superior  weight,  falling 
to  the  bottom. 

The  nature  of  the  flux  used  must  depend,  in  any  particular  case,  upon 
the  character  of  the  ore  that  is  used.  Most  iron  ores  occur  in  the  granite 
rocks,  and  therefore  the  gangue  (that  is,  the  earthy  matter  of  the  ore,)  is 
mostly  silica,  which  of  itself  is  very  infusible  (323),  but  forms  a  fusible 
mass  when  mixed  with  lime.  Limestone,  in  fragments,  is  therefore  intro- 
duced with  the  ore,  which  is  first  by  the  heat  changed  to  caustic  lime,  by 
expulsion  of  the  carbonic  acid ;  and  the  lime  then  unites  with  the  silica, 
producing  the  fusible  silicate  of  lime,  which,  at  the  Jfcgh  temperature, 
flows  freely,  and  allows  the  reduced  particles  of  iron  to  unite  in  a  mass. 

Occasionally,  an  iron  ore  occurs  in  a  limestone  region ;  and  then,  the 
lime  alone  being  also  infusible,  a  flux  of  silica  (sand)  is  required. 

When  a  sufficient  quantity  of  melted  iron  has  accumulated  in 
the  furnace,  it  is  drawn  off  by  an  aperture  at  the  bottom,  which 
is  opened  for  the  purpose.  After  the  iron  has  been  removed,  the 
slag,  formed  by  the  union  of  the  flux  with  the  earthy  matter  of 
the  ore,  is  also  drawn  off. 

The  accompanying  figure  represents  a 
section  of  a  blast-furnace,  which  is  used 
for  the  reduction  of  iron  ores.  It  is  usually 
built  of  stone,  thirty  or  forty  feet  high,  and 
.lined  inside  with  fire-brick.  The  charcoal, 
or  coke,  and  the  ore,  in  proper  proportion, 
with  the  necessary  flux,  are  thrown  in  at 
top ;  and  A  A  are  pipes  leading  from  a 
powerful  bellows,  worked  by  water  or  steam- 
power,  for  supplying  the  blast  of  air.  This 
air  thus  forced  in,  will,  of  course,  be  of  the 
same  temperature  as  the  external  atmo- 
sphere, and  constitute  the  cold  blast;  but  sometimes  the  hot 
blast  is  used,  in  which  case  the  tubes  are  so  arranged  over  the 
top  of  the  furnace  that  they  are  kept  hot  by  the  blaze  from  the 
burning  mass,  and  the  air,  passing  through  them,  becomes  heated, 
and  enters  the  fire  at  a  temperature  of  400°  or  600°. 

When  once  put  in  operation,  a  furnace  is  usually  kept  in  full 
employment  for  many  months,  until  repairs  are  needed ;  the  fuel, 

QUESTIONS. — What  is  used  for  flux  when  the  ore  is  dug  from  siliceous 
rocks  ?  Describe  the  blast-furnace  used  for  reducing  ores  of  iron.  How 
is  the  air  sometimes  heated  before  being  forced  into  the  furnace  ?  Is  a 
furnace,  when  once  heated,  kept  long  in  operation  ? 


Blast-Furnace. 


IRON. 


351 


with  a  proper  proportion  of  ore  and  flux,  being  regularly  supplied 
at  the  top. 

The  iron  obtained  by  this  process  is  thecas*  or  pig-iron of  com- 
merce, and  contains  a  considerable  quantity  of  carbon  and  other 
substances,  by  which  it  is  rendered  much  more  fusible  than  pure 
iron,  but  is  at  the  same  time  harder  and  more  brittle. 

It  receives  it  name  from  the  fact  that  it  may  be  cast,  or  melted, 
and  poured  into  moulds,  so  as  to  form  articles  of  any  desired  figure 
For  this  purpose,  a  pattern  of  the  desired  article  is  formed  of  wood, 
and  moulded  in  sand; 
and  the  melted  metal  is 
poured  into  the"  cavity 
thus  produced.  The 
iron  is  usually  melted  Pouring  Cast-iron, 

in  a  cupola  furnace,  and  drawn  off  in  vessels  lined  with  clay  (see 
figure),  from  which  it  is  conveniently  poured. 

To  convert  cast  into  malleable  iron,  it  is  exposed,  in  a  melted 
state,  to  a  current  of  air,  which  plays  over  its  surface,  or  is  forced 
through  it.  The  process  is  usually 
conducted  in  a  reverberatory  fur- 
nace, a  section  of  which  is  shown 
in  the  figure  in  the  margin.  Gr  is 
the  grate  upon  which  the  fire  is 
kindled,  and  H  H  the  hearth 
which  contains  the  melted  metal. 
As  the  blaze  from  the  fuel  passes 
to  the  chimney,  C,  it  comes  in 
contact  with  the  melted  iron,  and 
the  carbon  it  contains— and  per-  Puddling  Furnace, 

haps   other  impurities  —  is  gradually  burnt  out,  and  the   iron 
becomes  malleable.      This  process  is  called  puddling. 

But  it  is  not  absolutely  essential  that  cast-iron  should  be  fused 
in  order  to  be  changed  into  the  malleable  state.  When  small 

QUESTIONS. — What  is  the  kind  of  iron  obtained  by  the  process  de- 
scribed? Why  is  it  called  cast-iron?  How  is  it  fashioned  into  articles 
of  any  desired  form ?  How  is  cast-iron  converted  into  malleable  iron? 
May  small  articles  made  of  cast-iron  be  converted  into  malleable  irou 
without,  being  fused  ?  Describe  the  pi-ocess. 


352  IRON. 

articles  made  of  cast-iron  are  heated  for  a  time  in  contact  with 
powdered  oxide  of  iron  in  close  vessels,  they  are  converted  into 
malleable  iron,  and  still  retain  their  form  perfectly.  The  carbon 
is  gradually  extracted  by  the  oxygen  of  the  oxide  of  iron  used. 

433.  Properties. — We  have  already,  under  the  last  head,  in 
part  described  the  properties  of  iron.  It  is  a  hard  metal,  of  a 
peculiar  gray  color,  and  strong  metallic  lustre,  which  is  sus- 
ceptible of  being  considerably  heightened  by  polishing.  Heated 
to  redness,  it  becomes  very  soft  and  pliable,  and  is  easily  worked 
under  the  hammer,  which  gives  it  a  decidedly  fibrous  structure. 
When  malleable  iron  is  strongly  heated,  it  does  not  at  once 
change  to  the  liquid  state,  like  most  of  the  other  metals,  but 
becomes  soft  and  pasty  at  the  surface;  so  that  two  pieces  in  this 
state,  upon  being  hammered  or  firmly  pressed  together,  unite  in 
one  piece,  or  are  welded  together.  Iron  is,  perhaps,  all  things 
considered,  the  most  useful  metal  known,  and  it  is  owing  in  a 
great  measure  to  this  property,  in  which  it  is  peculiar ;  only  a 
few  other  metals  possessing  it,  in  an  inferior  degree. 

Iron  has  a  strong  affinity  for  oxygen,  and  exposed  to  the  air 
and  moisture,  it  rusts,  or  oxydizes.  Heated  intensely  in  the 
blacksmith's  forge,  or  in  the  flame  of  the  compound  blowpipe,  it 
burns  with  brilliancy.  The  same  effect  is  produced*by  igniting  a 
wire  in  a  receiver  of  oxygen  gas  (192),  or  dropping  iron-filings 
into  the  flame  of  a  spirit-lamp.  It  has  the  property  also  of  be- 
coming magnetic,  under  the  influence  of  another  magnet  (121), 
or  of  the  galvanic  current  (136).  But  pure  iron  loses  its  mag- 
netism when  the  influence  of  the  current  is  removed.  Some  of 
the  compounds  of  iron,  especially  steel  and  the  black  oxide,  how- 
ever, retain  their  magnetism  permanently. 

The  iron  of  commerce  is  never  pure,  but  contains  in  combination  more 
or  less  carbon,  and  other  substances. 

Perfectly  pure  iron  can  be  obtained  only  by  heating  one  of  the  oxides, 


QUESTIONS. — 433.  Describe  the  properties  of  iron.  How  is  malleable 
iron  affected  when  heated  to  redness?  Describe  the  process  of  welding. 
Are  there  other  metals  capable  of  being  welded?  What  is  said  of  the 
affinity  of  iron  for  oxygen  ?  How  is  it  affected  when  exposed  to  air  arid 
moisture?  How  may  iron  be  made  to  burn?  How  may  pure  iron  bo 
procured  ? 


IRON.  353 

ar  the  protochloride,  in  an  atmosphere  of  hydrogen.  For  this  purpose, 
the  same  apparatus  may  be  used  as  figured  in  paragraph  426  for  forming 
protoxide  of  manganese.  *  The  oxide  or  chloride  being  heated  by  a 
lamp,  is  decomposed  by  the  current  of  dry  hydrogen,  and  the  iron 
remains  as  a  grayish-black  powder,  which  may  take  fire  spontaneously 
if  the  air  be  admitted,  but  may  be  preserved  any  length  of  time  by  seal- 
ing the  tube  hermetically.  By  reducing  the  iron  in  a  porcelain  crucible, 
at  a  very  high  temperature,  it  may  be  obtained  in  a  solid  mass,  with  a 
metallic  lustre. 

434.  Steel  is  a  carbonide  of  iron.  It  is  formed  by  heating 
bars  of  malleable  iron  in  close  vessels  in  contact  with  charcoal, 
by  which  process  a  small  quantity  of  carbon  is  absorbed  and 
incorporated  with  the  iron.  This  process  is  called  cementation; 
and,  although  the  proportion  of  carbon  absorbed  by  the  iron  is 
small,  yet  very  important  changes  are  produced  in  its  properties. 
It  becomes  more  fusible,  and  may  now  be  melted  like  cast-iron, 
and  at  the  same  time  has  become  harder,  and  is  capable  of  being 
tempered,  that  is,  of  being  made  hard  or  soft,  at  pleasure.  This 
is  done  by  first  heating  the  article  to  redness,  and  then  cooling 
it  suddenly  by  plunging  it  into  cold  water,  or  oil,  by  which  it  is 
made  very  hard  and  brittle,  and  subsequently  heating  it  mode- 
rately, and  allowing  it  to  cool  slowly.  By  the  last  heating,  a 
partial  annealing  (336)  is  effected,  and,  if  the  operation  has  been 
well  conducted,  a  proper  degree  of  hardness  is  produced. 

Bars  of  steel,  from  the  cementation  process,  always  present  a 
blistered  surface,  occasioned  by  the  liberation  of  gaseous  mat- 
ter— probably  carbonic  oxide — within  their  substance ;  but  when 
the  metal  has  been  melted  and  cast  in  moulds,  it  has  a  per- 
fectly uniform  texture,  and  is  called  cast-steel. 

The  melting  of  blistered  steel,  to  form  cast-steel,  requires  a  very  high 
temperature,  and  is  performed  in  a  furnace,  a  vertical  section  of  which 
is  represented  by  the  first  figure  on  next  page.  A  is  a  small  rectangular 
chamber,  containing  the  crucible  and  fuel,  and  connects  with  the  chim- 
ney, C,  by  a  horizontal  flue,  B.  The  top  of  this  chamber  is  covered  with 
a  lid,  EF,  which  may  be  removed,  at  pleasure,  to  allow  the  introduction 
of  the  fuel  and  the  crucibles,  and  the  current  of  air  is  regulated  by  a 
iamper,  B,.  The  crucibles  are  made  of  'the  most  refractory  clays,  and 
of  the  form  represented  in  the  second  figure.  When  the  steel  is  perfectly 

QUESTIONS. — 434.  What  is  steel  ?  How  is  it  formed  ?  In  what  does  it 
differ  from  iron  in  its  properties?  How  afre  bars  of  blistered  steel  con- 
verted into  cast-steel  ?  How  are  articles  made  of  steel  tempered  ?  What 
is  meant  bv  this  ? 

80* 


354 


IRON. 


fused,  the  crucible  is  withdrawn,  and  the  melted  metal  poured  into  iron 
ingot-  iioulds  prepared  for  the  purpose. 


Melting  Furnace. 


Crucible. 


Binary  Compounds  of  Iron. 

435.  Oxides  of  Iron.  —  There  are  four  oxides  of  iron,  as 
follows,  viz : — 

The  protoxide,  FeO,  which  is  a  powerful  base. 

The  sesquioxide,  Fe203,  which  is  a  feeble  base,  isoraorphous 
with  alumina,  A1203.  It  is  often  called  the  peroxide. 

The  oxide,  Fe304,  called  also  black  or  magnetic  oxide,  which  is 
considered  a  compound  of  the  proto  and  sesquwxides ; — thus, 
FeO  -f  Fe203  =  Fe304.  It  belongs  to  the  class  of  "  saline 
oxides"  (344  : 4). 

Ferric  acid,  Fe03. 

The  red,  or  sesquioxide  of  iron,  is  obtained  by  heating  green 
vitriol  (sulphate  of  the  protoxide  of  iron)  to  redness  in  the  open 
air,  and  is  used  as  a  polishing-powder,  under  the  name  of  rouge 


QUESTIONS. — 435.  Describe  the  oxides  of  iron, 
qui  oxide  obtained  ? 


How  is  the  red  or  ses- 


IRON.  355 

or  colcothar.  Earth  or  clay  highly  impregnated  with  it  forms 
the  red  ochre  used  by  painters.  The  black  oxide  constitutes  the 
scale  that  always  forms  upon  the  surface  of  iron  when  heated  to 
redness  ^in  the  open  air.  Large  accumulations  of  it  are  often  seen 
by  the  side  of  the  smith's  anvil.  This  oxide,  found  native,  con- 
stitutes the  native  magnet,  or  loadstone,  as  stated  above.  It  is 
found  crystalized  in  beautiful  octahedrons,  and  in  masses,  and  is 
one  of  the  best  ores  of  the  metal.  . 

Ferric  acid,  Fe03,  in  combination  with  potash,  as  ferrate  of  potash,  is 
formed  by  heating  a  mixture  of  iron-filings  and  nitrate  of  potash  in  an 
iron  crucible ;  and  the  salt  may  be  separated  from  the  mass  by  treating 
it  with  cold  water.  It  cannot  be  obtained  in  a  separate  state. 

436.  Chlorides  of  Iron. — There  are  two  chlorides  of  iron,  the  proto- 
chloride,  FeCl,  and  the  sesquichloride,  Fe2Cl3 ;  the  first  may  be  obtained 
by  dis'solving  iron  in  hydrochloric  acid,  and  the  second  by  treating  the 
sesquioxide  in  the  same  manner.     They  possess  no  particular  interest. 

437.  Sulphides  of  Iron. — The  protosulphide,  FeS,  of  iron  is 
readily  formed  by  heating  a  mixture  of  iron-filings  and  sulphur, 
or  by  pressing  a  bar  of  iron  heated  to  whiteness  into  a  mass  of 
sulphur.     The  sulphur  and  iron  combine  with  great  energy,  and 
the  liquid  sulphide  collects  in  a  mass  at  the  bottom,  forming,  on 
cooling,  a  hard,  brittle  solid.     It  is  used  in  preparing  hydrosul- 
phuric  acid  (263). 

Bisulphide  of  iron,  FeS2,  is  the  iron  pyrites  of  mineralogists. 
It  is  of  a  beautiful  yellow  color,  resembling  gold,  for  which  it  has 
often  been  mistaken.  It  is  usually  crystalized  in  cubes.  It  is 
used  in  the  manufacture  of  green  vitriol  and  sulphuric  acid;  and 
sometimes  for  extracting  its  sulphur. 

Though  the  sulphides  of  iron  are  very  abundant  in  nature,  they 
cannot  be  used  for  the  extraction  of  the  metal,  because  of  the 
great  expense  it  requires,  and  the  iron  obtained  is  of  an  inferior 
quality. 

438.  Carbonides  of  Iron. — Both  cast-iron  and  steel,  as -we  have 
seen,  are  considered  as  carbonides  of  iron,  but  the  ingredients  do 

QUESTIONS. — What  is  the  red  ochre  of  painters  ?  What  is  the  natural 
magnot,  or  loadstone  f  436.  Describe  the  chlorides  of  iron.  437.  Describe 
the  sulphides  of  iron.  How  may  the  protosulphide  be  formed  ?  FOP 
what  is  the  bisulphide  sometimes  mistaken?  438.  What  is  said  of  the 
carbonides  of  iron  ? 


356  SALTS     OF    IRON. 

not  seem  to  be  united  exactly  in  definite  proportions.  Cast-iron 
usually  contains  from  2  to  5  per  cent,  of  carbon,  while  steel 
seldom  contains  as  much  as  2  per  cent.  Graphite,  called  also 
plumbago,  and  black  lead,  has  been  considered  as  a  carbgnide  of 
iron,  but  probably  it  is  only  a  particular  form  of  carbon,  usually 
containing  a  portion  of  iron  as  an  accidental  impurity.  It  is 
found  abundantly  in  nature,  and  is  used  in  the  manufacture  of 
pencils  and  crucibles,  and  as  a  polishing-powder  for  stoves  and 
other  articles  made  of  iron. 

Protiodide  of  iron,  Fel,  is  formed  by  digesting  iron-filings  or  wire  in 
water  containing  iodine,  and  evaporating  the  solution  obtained.  It  is 
used  in  medicine. 

Salts  of  Iron. 

439.  Carbonate  of  Iron,  FeO,C02,  occurs  native  and  is  called 
spathic  iron,  or  steel  ore,  by  mineralogists.     An  impure  variety 
is  called  clay-iron  stone.     It  may  also  be   obtained  by  adding 
solu-tion  of  carbonate  of  soda  to  solution  of  green  vitriol.     Car- 
bonate of  iron,  though  insoluble  in  pure  water,  is  dissolved  by 
water  charged  with  carbonic  acid,  and  is  thus  contained  in  the 
water  of  chalybeate  springs. 

440.  Sulphate  of  iron,  FeO,S03. — This  salt  is  the  green  vitriol 
or  copperas  of  commerce,  so  extensively  used  in  the  arts.     In  crys- 
tals it  contains  7  eq.  of  water,  and  its  formula  of  course  is  FeO,S03 
4-7HO.     The  crystals  belong  to  the  monoclinic  system.     It  is  a 
sulphate  of  the  protoxide,  and  is  prepared  on  a  large  scale  at 
Strafford,  Vermont,  and  other  places,  from   iron  pyrites,  which 
is  first  roasted  slightly,  and  then  exposed  in  heaps  to  the  atmo- 
sphere, from  which  oxygen  is  absorbed,  converting  the  sulphur 
into  sulphuric  acid,  and  the  iron  into  oxide  of  iron;   the  two 
together  then  uniting  to  form  the  salt  in  question.     For  use  in 
the  laboratory,  it  is  readily  formed  by  the  action  of  dilute  oil  of 
vitriol  upon  metallic  iron.     It  often  forms  upon  specimens  of 

QUESTIONS. — What  is  graphite?  439.  Is  carbonate  of  iron  found  na- 
tive? What  is  it  called  by  mineralogists?  440.  What  is  the  green 
vitriol  or  copperas  of  commerce  ?  How  is  it  manufactured  in  Vermont  ? 
What  use  is  made  of  it  ? 


CHROMIUM.  857 

:ron  ores  contained  in  cabinets,  by  the  action  of  the  atmosphere, 
md  is  seen  as  a  yellowish-white  powder. 

It  is  used  in  coloring  black,  and  in  the  manufacture  of  writing- 
ink,  and  for  other  purposes. 

When  this  salt  is  heated  it  first  parts  with  its  water,  and  at 
a  full  red  heat,  with  its  sulphuric  acid,  a  portion  of  which  is  de- 
composed into  sulphurous  acid  and  oxygen,  but  the  rest  passea 
off  unchanged.  By  the  oxygen  of  the  decomposed  acid,  the 
iron  is  peroxydized,  forming  the  colcothar  of  commence,  before 
mentioned. 

441.  Nitrate  of  Iron,  FeO,N05. — Nitric  acid  acts  readily  upon  iron,  and 
at  the  same  time  •with  the  nitrate  of  iron  there  is  formed  also  nitrate  of 
ammonia,  the  ammonia  being  produced  by  the  union  of  a  portion  of  the 
nitrogen  of  the  acid  with  the  hydrogen  of  the  water.     The  nitric  acid 
should  be  considerably  diluted. 

442.  Tests  of  Iron.— The  usual  test  for  iron  is  solution  of  yel- 
low prussiate  of  potash,  which  forms  with  it  a  beautiful  blue.     For 
an  experiment,  let  a  small  quantity  of  common  hydrochloric  acid 
be  largely  diluted  with  water,  and  then  pour  into  it  a  few  drops 
of  solution  of  this  prussiate,  which  will  instantly  give  a  fine  sky- 
blue  color  if  iron  be  present  in  the  acid,  as  is  almost  certain  to  be 
the  case.     The  iron  is  derived  from  the  utensils  made  use  of  in 
the  manufacture  of  the  acid. 

With  tincture  of  nutgalls,  the  soluble  salts  of  iron  form  at  first 
a  dark-blue  precipitate,  which  finally  becomes  black. 


CHROMIUM. 

Symbol,  Cr;  Equivalent,  26  -7;  Density,  6. 

443.  iKistory,  Etc. — Chromium  was  discovered  in  1797.  It 
is  found  in  considerable  abundance  in  Massachusetts,  Penn- 
sylvania, and  other  States,  in  the  mineral  called  chrome  iron, 
and  also  in  combination  with  oxide  of  lead.  Its  name  comes 
from  the  Greek  chroma,  color,  in  allusion  to  the  splendid  color 

QUESTIONS. — 441.  How  is  nitrate  of  iron  formed?  442.  What  tests 
of  iron  are  mentioned  ?  443.  What  is  said  of  chromium  ?  From  what  is 
the  name  derived  ? 


358  SALTS    OP    CHROMIC    ACID. 

of  many  of  its  compounds.  It  is  prepared  by  heating  its  oxides 
mixed  with  charcoal,  but  not  without' difficulty.  The  metal  has 
a  white  color,  and  distinct  metallic  lustre.  It  is  very  brittle,  and 
with -difficulty  fusible. 

Metallic  chromium  is  not  used  in  the  arts,  but  several  of  its 
compounds  are  important. 

Binary  Compounds  of  Chromium. 

444.  Oxides  of  Chromium, — Oxygen  forms  several  compounds 
with  chromium,  which,  in  composition  and  many  of  their  pro- 
perties, are  analogous  to  the  oxides  of  iron  and  manganese ;  so 
that  these  three  metals  form  a  kind  of  natural  family,  in  the  same 
manner  as  potassium,  sodium,  and  lithium.  Only  two  of  these 
oxides,  the  sesquioxide,  Cr203,  and  the  teroxide,  or  chromic  acid, 
Cr03,  are  of  sufficient  importance  to  claim  attention  here. 

The  former  of  these,  Cr203,  in  combination  with  protoxide  of  iron,  form- 
ing the  compound,  FeO,Cr203,  constitutes  the  native  chromic  iron,  which 
is  the  most  abundant  ore  of  the  metal.  It  may  be  prepared  by  various 
modes,  but  the  following  is  perhaps  the  best,  as  it  leaves  the  oxide  in  a 
proper  state  for  use  in  the  arts.  Heat  in  a  crucible  an  intimate  mixture 
of  4  parts  of  bichromate  of  potash  and  1  part  of  starch,  and  wash  the 
mass  thoroughly  with  hot  water,  to  separate  the  carbonate  of  potash  that 
has  been  formed.  The  residue,  after  being  dried,  is  again  heated,  and 
the  pure  sesquioxide  remains. 

Sesquioxide  of  chromium  is  not  decomposed  by  heat,  and  when  fused 
with  fluxes,  it  imparts  to  them  a  green  color.  It  is  used  in  staining  glass 
and  porcelain.  It  replaces  alumina  (415)  in  the  chromic  alums. 

Chromic  acid  Cr03,  is  prepared  by  decomposing  a  saturated  solution 
of  bichromate  of  potash  with  1£  times  its  volume  of  oil  of  vitriol ;  bisul- 
phate  of  potash  is  form'ed,  and  the  chromic  acid  separates  in  brilliant 
red  crystals,  which  are  very  soluble  in  water,  and  deliquescent  in  the  air. 
It  is  a  powerful  oxydizing  agent,  and  strong  alcohol  thrown  upon  the  dry 
crystals  is  very  soon  inflamed.  With  bases  it  forms  important  salts. 

The  chlorides  and  sulphides  of  chromium  are  not  important. 

Salts  of  Chromic  Acid. 

445.  The  Chromates  of  Potash  are  formed  by  heating  a  mix- 
ture of  native  'chrome  iron  in  powder  with  nitre,  digesting  the 

QUESTIONS. — 444.  What  is  said  of  the  oxides  of  chromium  ?  How  may 
the  sesquioxide  be  formed?  How  is  chromic  acid  prepared?  What  is 
said  of  the  action  of  alcohol  upon  it?  445.  How  is  bichromate  of  potash 
formed  ? 


ZINC.     ,  359 

mass  obtained  in  hot  water,  and  saturating  the  solution  with  dilute 
sulphuric  acid.  After  a  little  time  the  clear  red  liquid  is  poured 
off  and  evaporated,  when  crystals  of  bichromate  of  potash,  KO, 
2Cr03,  are  separated,  from  the  excess  of  sulphuric  acid  present, 
and  the  sulphates  of  iron  and  alumina. 

The  neutral  chromate  of  potash,  KO,Cr03,  is  now  easily  pro- 
cured by  neutralizing  a  solution  of  the  bichromate  with  carbonate 
of  potash,  and  crystalizing. 

The  bichromate,  which  is  of  a  deep  red  color,  is  much  used  in 
dyeing,  and  in  calico-printing,  and  for  many  purposes  in  the 
chemical  laboratory. 

446.  Chromate  of  Lead,  PbO,Cr03.  —  This  is  the  beautiful 
chrome  yellow,  used  as  a  paint.  It  is  formed  by  mixing  solutions 
of  one  of  the  chromates  of  potash  and  acetate  or  nitrate  of  lead. 
The  beauty  of  the  color  will  depend  somewhat  on  the  strength 
of  the  solutions  used,  and  other  circumstances.  Chrome  green  is 
formed  by  mixing  the  chromate  of  lead  with  Prussian  blue,  in  a 
particular  stage  of  the  process  of  manufacture. 


ZINC. 
Symbol,  Zn;  Equivalent,  32-5;  Density,  7. 

447.  History. — This  metal  has  been  known  several  centuries, 
but  was  not,  for  many  years,  much  used.     Its  chief  ores  are 
calamine,  which  is  a  native  carbonate,  and  blende,  which   is  a 
sulphide;  but  several  others  are  known.     These  ores  are  found 
in  considerable  abundance  in  New  Jersey,  and  other  parts  of  this 
country. 

448,  Preparation.  —  The  ores  of  zinc  are  reduced  by  first 
roasting  them  in  the  open  air,  and  then  distilling  them  with 
charcoal  in  close  crucibles,  from  which  a  tube  descends  directly 

QUESTIONS. — How  is  the  neutral  chromate  of  potash  formed  ?  446.  De- 
scribe the  mode  of  preparing  chromate  of  lead.  By  w^fttxetime  is  it 
familiarly  known  ?  What  use  is  made  of  it  ?  How  is  chrome  green  pre- 
pared? 447.  Has  zinc  been  long  known?  What  ores  of  it  are  men- 
tioned ?  448.  Describe  the  mode  of  reducing  the  metal  from  its  ores. 


360 


ZINO 


through  the  bottom.  The  metal  is  volatilized  by  the  heat,  and 
descends  through  the  tube,  from  which  it  is  received  into  a 
vessel  of  water.  The  necessity  of  excluding  the  air  perfectly, 
arises  from  the  fact  that  vapor  of  zinc,  on  coming  in  contact 
with  the  oxygen  of  the  air,  is  at  once  oxydized;  and  the 
object  of  having  the  tube  which  conveys  away  the  volatilized 
metal  pass  directly  downward,  is,  to  preserve 
its  temperature  so  high  that  it  shall  not  be- 
come clogged  by  the  condensed  metal. 

The  figure  in  the  margin  represents  the  section 
of  a  crucible  used  for  this  purpose,  with  its  charge 
of  ore  and  charcoal,  and  tube  made  of  fire-clay 
passing  downward  through  the  bottom.  The  cover 
is  carefully  luted  on,  and  it  is  supported  a  little 
above  the  grate  of  the  furnace  by  a  fire-brick. 
The  zinc,  as  it  is  separated  from  the  ore,  taking 
the  gaseous  state,  passes  downward  through  the 
tube  into  a  basin  of  water  placed  below  to  receive 
it.  The  part  of  the  tube  below  the  bottom  of  the 
crucible,  not  being  surrounded  by  the  fire,  remains 
comparatively  cold  ;  and  the  metal,  before  it  reaches 
the  water,  is  condensed  to  the  liquid  state,  and  falls 
in  drops  into  the  water. 

Commercial  zinc  usually  contains  iron,  lead,  and 
other  impurities,  from  most  of  which  it  may  be 
separated  by  distillation  in  this  manner. 

449.  Properties.  —  Zinc  has  a  -bluish-white  color  and  a  strong 
metallic  lustre.  In  masses,  it  always  has  a  highly  crystaline 
structure,  and  in  commerce  it  is  called  spelter.  When  cold  it  is 
quite  brittle;  but  heated  to  about  300°,  it  becomes  malleable, 
and  may  be  rolled  into  thin  sheets.  Heated  to  773°,  it  melts; 
at  a  little  higher  temperature,  in  the  open  air,  it  takes  fire  and 
burns  with  a  brilliant  white  flame,  producing  the  protoxide,  which 
assumes  an  exceedingly  delicate  gossamer  appearance,  and  has 
been  called  nihil  album,  pJiilosophers'  wool,  and  by  other  names. 

Zinc  is  much  used  in  the  arts,  in  the  preparation  of  brass,  in 
the  construction  of  galvanic  batteries,  and,  rolled  in  thin  sheets, 
as  a  substitute  for  sheet-iron  and  tin-plate.  Recently  it  has  been 


Crucible  for  reducing 
Zinc 


is  it  necessary  to  exclude  the  air?  Describe  the 
form  of  crucible  used  in  reducing  these  ores.  449.  Describe  the  pro- 
perties of  zinc.  What  is  its  melting  point?  What  is  produced  when  it 
is  highly  heated  in  the  open  air  ?  What  use  is  made  of  zinc  ? 


SALT  8    OF    ZINC.  361 

considerably  used  as  a  coating  for  sheet-iron,  in  the  same  manner 
as  tin,  to  protect  it  from  oxydation.  The  iron  thus  prepared  is 
known  in  the  arts  as  galvanized  iron. 

Binary  Compounds  of  Zinc. 

450.  Protoxide  of  Zinc,  ZnO. — This  is  the  only  oxide  of  zinc 
known.     It  is  of  a  yellowish-white  color,  and  may  be  prepared,  as 
above  described,  by  heating  zinc  in  the  open  air,  or  by  precipi- 
tating it  from  solution  of  white  vitriol  (sulphate  of  zinc)  by  car- 
bonate of  ammonia.     It  is  much  used  in  painting  as  a  substitute 
for  white  lead ;  and  is  manufactured  on  a  large  scale  directly  from 
the  ores  of  zinc,  in' France,  and  in  New  Jersey. 

451.  Chloride  of  Zinc,  ZnCl. — Chloride  of  zinc  is  formed  by 
dissolving  commercial  zinc  in  hydrochloric  acid,  or  by  burning 
zinc  in  chlorine  gas.     By  evaporation  it  may  be  obtained  as  a 
white  solid,  but  is  very  deliquescent  in   the  air.      Mixed  with 
sal-ammoniac,  it  serves  an  excellent  purpose  in  tinning  articles 
of  copper,  brass,  and  other  metals. 

Sulphide  of  Zinc,  ZnS. — This  compound  of  zinc  is  found  native,  and 
constitutes,  as  has  been  stated,  one  of  its  ores.  It  may  be  prepared  arti- 
ficially by  heating  the  metal  with  sulphur. 

*        Salts  of  Zinc. 

There  are  several  salts  of  zinc,  but  the  most  important  is  the 
following : — 

452.  Sulphate  of  Zinc,  ZnO,S03. — Sulphate  of  zinc  is  a  white 
salt,  which,  in  commerce,   is  called  white  vitriol.      It  is  very 
soluble  hi  water ;  and  is  sometimes  used  in  medicine  as  a  power- 
ful emetic. 

The  ordinary  salt  contains  7  atoms  of  water  of  crystalization, 
and  its  formula  is  ZnO,S03  +  7HO;  but  by  using  the  proper 
means,  it  may  be  crystalized  with  5,.  2,  or  even  1  atom  of  water. 

QUESTIONS. — 450.  What  is  the  only,  oxide  of  zinc  that  is  known  ?     What 
use  is  made  of  it?     451.  How  is  chloride  of  zinc  formed?     To  what  use 
is  it  applied  ?    452.  What  is  sulphate  of  zinc  called  in  commerce  ? 
31 


362  CADMIUM. — TIN. 

Oxide  of  zinc  is  precipitated  from  its  soluble  salts  by  the  caustic  alka- 
lies, but  the  precipitate  is  again  dissolved  by  an  excess  of  the  alkali. 
Carbonate  of  zinc  is  found  native,  and  called  calamine. 


CADMIUM. 

Symbol,  Cd;  Equivalent,  56;  Density,  8-6. 

453.  History,  Etc, — Cadmium  is  a  very  volatile  metal,  usually 
found  associated  with  zinc.  In  appearance  it  can  scarcely  be  distin- 
guished by  the  eye  from  tin,  but  is  rather  harder.  It  melts  at  442°, 
— the  melting  point  of  tin, — and  sublimes  at  a  temperature  but  little 
above  the  boiling  point  of  mercury.  Its  properties  indicate  that 
it  would  be  a  useful  metal  in  the  arts,  but  it  has  hitherto  been 
found  only  in  small  quantities. 

Protoxide  of  Cadmium,  CdO,  is  the  only  compound  of  these  two  elements 
that  is  known. 

The  protosulphide,  CdS,  is  found  native,  as  thegrenockite  of  mineralogists. 


TIN. 

Symbol,  Sn  ^Stannum);  Equivalent,  58;  Density,  7 '3. 

454.  History.  —  Tin  has  been  known  from  the  most  remote 
antiquity,  and  was  in  common  use  in  the  time  of  Moses.     It  is 
supposed  the  ancients  obtained  it  chiefly  from  Cornwall,  England, 
the  mines  of  which  still  yield  a  large  part  of  the  tin  of  commerce. 
It  is  found  also  in  India,  Germany,  Chili,  and  Mexico ;  but  has 
not  yet  been  discovered  in  the  United  States,  except  a  few  small 
crystals  of  the  oxide  in  Chesterfield,  Massachusetts,  and  at  Mid- 
dletown,  Connecticut,  and  a  small  vein  of  the  same  ore  in  the 
town  of  Jackson,  New  Hampshire.     The  chief  ores  are  the  oxide 
and  sulphide. 

455.  Preparation  and  Properties.  —  Most  of  the  tin  of  com- 
merce is  obtained  from  the  oxide,  which  is  reduced  by  the  action 

QUESTIONS. — 453.  What  is  said  of  cadmium?  What  is  its  melting 
point?  454.  Has  tin  been  long  known?  Where  was  it  obtained  in 
ancient  times  ?  What  countries  now  produce  tiij  ?  Is  it  found  in  the 
United  States  ?  What  are  the  chief  ores  of  tin  ?  455.  Mention  some 
of  its  more  important  properties. 


BINARY     COMPOUNDS     OP    TIN.  363 

of  charcoal  at  a  high  temperature.  It  is  a  brilliant  white  metal, . 
like  silver,  but  is  less  hard  than  the  latter  It  is  very  malleable, 
and  is  rolled  into  very  thin  leaves,  called  tin-foil.  It  is  inelastic, 
and  when  a  rod  of  it  is  bent,  a  peculiar  crackling  noise,  called  the 
cry  of  tin,  is  produced,  occasioned  by  its  crystaline  structure.  It 
melts  at  442°,  and  at  a  red  heat  is  rapidly  oxydized;  at  a  whi^ 
heat  it  burns  with  flame. 

Tin  is  not  readily  acted  on  by  the  atmosphere  or  by  moisture,  bu 
dissolved  slowly  by  hydrochloric  acid,  forming  chloride  of  tin,  and  b. 
hot  sulphuric  acid,  forming  sulphate  of  the  protoxide ;  by  dilute  nitric 
acid  it  is  converted  into  the  binoxide,  which  is  insoluble  in  the  acids. 

Uses. — Tin  is  used  for  many  purposes,  in  the  arts,  both  alone 
and  combined  with 'other  metals,  as  in  Britannia  metal,  which  is 
an  alloy  of  tin  and  antimony,  with  a  small  proportion  of  copper. 
It  is  also  used  extensively  to  coat  sheets  of  copper  and  iron,  to 
prevent  the  oxydizing  influence  of  the  air  and  moisture,  and  other 
agents.  Thin  sheets  of  iron,  coated  over  with  tin,  constitute  the 
well-known  and  highly  useful  tin-plate. 

Binary  Compounds  of  Tin. 

456.  Oxides  of  Tin.  —  There  are  two  well-defined  oxides  of  tin,  the 
protoxide,  SnO,  and  the  peroxide,  SnOa;  but  the  latter  alone  possesses 
sufficient  importance  to  require  a  description. 

Peroxide  of  Tin  is  formed  by  exposing  the  metal  to  the  action  of  nitric 
acid  a  little  diluted.  It  may  also  be  precipitated  from  a  solution  of  the 
perchloride  of  tin  (soon  to  be  described)  by  an  alkali.  As  obtained  by 
the  mode  last  mentioned,  it  is  soluble  in  acids,  but  not  as  procured  by  the 
other  mode.  It  is  of  a  yellowish-gray  color,  and  from  the  circumstance 
that  it  is  capable  of  combining  with  bases  in  the  manner  of  an  acid,  it 
has  been  called  stannic  acid.  It  is  much  used  as  a  polishing-powder, 
under  the  name  of  putty  of  tin.  Melted  with  ingredients  for  forming 
glass,  it  produces  a  white  enamel. 

457.  Chlorides  of  Tin. — Protochloride  of  Tin,  SnCl,  is  formed  by  dis- 
solving the  metal   in  boiling   hydrochloric  acid.      By  evaporating  the 
solution  it  may  be  obtained  in  crystals,  which  contain  2  eq.  of  water. 
It  is  used  as  a  mordant  in  dyeing,  and  as  a  powerful  deoxydizing  agent 
in  the  laboratory.     The  perchloride,  SnCl2,  is  formed  by  distilling  a  mix- 
ture of  1  part  of  tin-filings  and  3  parts  of  corrosive  sublimate,  or  by  cau- 

QUESTIONS. — To  what  use  is  tin  applied  ?  What  is  the  tin-plate  of  com- 
merce? 456.  What  oxides  of  tin  are  known?  What  is  the  substance 
called  putty  of  tin?  To  what  use  is  it  applied?  457.  What  chlorides 
»f  tin  are  there  ? 


364  COBALT. — BINARf   COMPOUNDS   OF   COBALT. 

tiously  dissolving  the  metal  in  nitre-hydrochloric  acid.  It  is  much  used 
as  a  mordant  in  dyeing,  and  as  a  disinfecting  agent. 

There  are  two  sulphides  of  tin; — the persulphide,  SnS2,  sometimes  called 
aurum  musivum,  or  mosaic  gold,  has  a  yellow  color,  and  metallic  lustre, 
and  is  used  as  a  paint,  and  also  instead  of  the  zinc  amalgam  (90)  for 
exciting  electrical  machines. 

There  are  no  important  salts  of  tin. 


COBALT. 

Symbol,  Co;  Equivalent,  29 -5;  Density,  8-5. 

458.  History,  Etc. — Cobalt  is  almost  always  found  associated 
with  nickel,  the  metal  next  to  be  described ; — as  found  in  mines 
both  are  usually  in  combination  with  arsenic.     The  pure  metal 
is  obtained  with  some  difficulty.     The  best  mode  is  to  heat  oxa- 
late  of  cobalt  in  a  small  crucible,   on  which  a  cover  is  closely 
luted.     It  is  of  a  reddish-white  color,  and  is  hard  and  brittle,  and 
difficult  to  fuse.     It  is  capable  of  becoming  magnetic. 

Cobalt  is  comparatively  a  rare  metal.  In  combination  with  arsenic,  it 
is  found  at  Chatham,  in  Connecticut,  in  the  minerals  called  smaltine  and 
chloanthite. 

Binary  and  Other  Compounds  of  CoLalt. 

459.  Oxides  of  Cobalt. — There  are  two  oxides  of  cobalt,  the  protoxide, 
CoO,  and  the  sesguioxide,  Co203,  the  former  of  which,  mixed  with  some 
impurities,  is  sold  in  commerce  as  a  gray  powder,  under  the  name  of 
zaffre.     Fused  with  silica  and  potash,  it  forms  smalt,  which  is  used  for 
coloring  glass,  porcelain,  &c.,  blue.     The  sesqui  or  peroxide  is  unimportant. 

460.  Chloride  of  Cobalt,  CoCl,  is  formed  by  dissolving  zaffre  in  hydro- 
chloric acid.     The  solution  has  a  pink  color,  and  yields  by  evaporation 
small  crystals  of  the  same  tint.     Writing  made  with  a  diluted  solution 
of  it  is  nearly  invisible,  but  becomes  of  a  beautiful  but  pale  blue  color 
when  the  paper  is  warmed  by  the  fire,  and  again  disappears  as  the  paper 
cools.     It  has  been  called  Hellofs  Sympathetic  Ink.     The  addition  of  a 
salt  of  nickel  gives  the  writing  a  green  color. 

The  salts  of  cobalt  possess  no  especial  interest.  The  subcarbonate  is  a 
fine  powder  of  a  very  delicate  pink  tint. 

QUESTIONS. — What  sulphides  of  tin  are  there  ?  458.  With  what  other 
metal  is  cobalt  usually  found  associated  ?  Where  is  this  metal  found  ? 
469.  What  oxides  of  cobalt  are  there  ?  460.  How  is  chloride  of  cobalt 
formed  ?  Describe  the  mode  of  using  Hellot's  Sympathetic  Ink 


NICKEL. — ANTIMONY.  365 

4     NICKEL. 

Symbol,  Ni;  Equivalent,  29-6 }  Density,  8-8. 

461.  History,  Etc. — Nickel  and  cobalt,  as.  before  intimated; 
are  in  nature  almost  inseparable  companions.  Arsenical  nickel 
and  cobalt  are  found  at  Chatham,  in  Connecticut,  and  also  in 
Missouri,  and  in  various  places  in  Europe ;  but  mines  of  these 
metals  are  not  common.  Nickel  is  generally,  if  not  always,  com- 
bined with  meteoric  iron  (431),  of  the  mass  of  which  it  sometimes 
constitutes  as  much  as  ten  per  cent. 

Pure  nickel  has  a  grayish-white  color,  and  strong  metallic 
lustre.  It  is  quite  hard,  but  malleable,  and  is  nearly  as  difficult 
to  melt  as  iron.  Like  iron  and  cobalt,  it  is  capable  of  becoming 
magnetic.  It  is  not  readily  acted  upon  by  the  air  or  by  moisture. 
It  is  much  used  in  the  arts  to  form  the  alloy  called  German 
silver,  which  is  composed  of  copper  10  parts,  zinc  6,  and  nickel  4. 

None  of  the  compounds  of  nickel  possess  sufficient  interest  to 
require  description  here. 


GROUP  V. 
ANTIMONY 


BISMUTH 

.LEAD 

JOPPE-R 

VANADIUM 

MOLYBDENUM 

TUNGSTEN 

TITANIUM 

URANIUM  ' 

COLUMBIUM 

PELOPIUM 


Metals  which  are  incapable  of  decomposing  water,  and 
whose  oxides  are  not  reduced  by  the  mere  action  of  heat. 

All  of  them,  except  lead  and  copper,  are  brittle ;  and 
all,  except  antimony,  bismuth,  lead,  and  copper,  are 
fusible  only  at  very  high  temperatures. 


ANTIMONY. 

Symbol,  Sb  (Stibium}',  Equivalent,  129';  Density,  67. 

462.  History.  —  Antimony  is  remarkable  as  having  been  the 
first  metal  discovered  after  the  seven  metals  (332)  known  to  the 

QUESTIONS. — 461.  What  is  said  of  the  metal  nickel  ?     In  what  is  it 
almost  always  found?     Describe  the  metal.     For  what  is  it  used?  .  How 
are  the  metals  of  Group  V.  characterized  ?     Name  the  metals  of  this 
group.     462.  For  what  is  antimony  remarkable  ? 
31* 


366  BINARY    COMPOUNDS    OF    ANTIMONY. 

ancients.     It  has  been  found  in  the  metallic  state,  but  is  prepared 
chiefly  from  the  sulphide,  which  is  not  of  unfrequent  occurrence. 

463.  Preparation. — The  metal,  called  also  reyulus  of  antimony, 
is  obtained  by  heating  the  sulphide  with  iron-filings,  or  carbonate 
of  potash.     When  iron-filings  are  used,  the  sulphur  is  simply 
transferred  from  the  antimony  to  the  iron,  and,  of  course,  sul- 
phide of  iron  is  formed;   but  the   metal   thus  obtained  always 
contains  a  portion  of  iron,  and  is  otherwise  impure.     By  the 
other  process,  the  sulphur  is  converted  into  sulphuric  acid,  which 
combines  with  the  potash,  forming  sulphate  of  potash ;  and  the 
metallic  antimony,  being  thus  set  free,  falls  to  the  bottom  of  the 
crucible. 

464.  Properties. — Antimony  is  a  very  brittle  metal,  of  a  white 
color,  and  brilliant   lustre.     It  always  has  a  highly  crystaline 
structure,  and  melts  at  a  temperature  a  little  below  redness ;  and 
may  be  slowly  distilled  in  a  current  of  hydrogen  gas.     A  small 
fragment,  heated   on  a  piece  of  charcoal,  before  the  blowpipe, 
takes  fire ;  and  when  thrown  upon  the  floor  breaks  into  numerous 
globules,  which  continue  to  burn  as  they  are  scattered,  leaving  a 
train  to  mark  their  path,  and  filling  the  air  with  fumes  of  the 
oxide. 

465.  Alloys  of  Antimony. — Antimony,  being  very  brittle,  is 
not  adapted  for  use  alone  in  the  arts,  but  with  other  metals  it 
forms  several  very  useful  alloys.     One  of  these,  called  Britannia 
metal,  is  composed,  of  tin  88  or  90  parts,  and  antimony  12  to  10 
parts.      Sometimes  a  small  proportion  of  copper  is   added,  not 
exceeding  3  or  4  per  cent,  of  the  whole. 

Its  alloy  with  lead  will  be  described  hereafter. 

Binary  Compounds  of  Antimony. 

466.  Oxides  of  Antimony.  —  Antimony  forms  with  oxygen  two  com- 
pounds which  are  well-defined,  viz.,  oxide  of  antimony,  SbOs,  and  and- 
monic  acid,  Sb06;  but  these  are  capable  of  combining  with  each  other  so 
as  to  form  one  or  two  other  intermediate  compounds. 

QUESTIONS. — 463.  How  is  antimony  obtained  from  the  native  sulphide  ? 
Describe  the  two  processes.  464.  Describe  the  metal.  How  is  it  affected 
When  intensely  heated  in  the  air?  465.  What  alloys  of  antimony  are 
used  in  the  arts  ?  466.  What  oxides  of  antimony  are  mentioned  ? 


BISMUTH.  367 

467.  Chlorides  of  Antimony.  —  There  are  two  chlorides  of  antimony, 
SljCl3,  and  SbC'5,  corresponding  in  composition,  it  will  be  seen,  with  the 
oxides.  The  terchloride,  Sb013,  is  sometimes  called  butter  of  antimony. 
It  is  soluble  in  a  small  quantity  of  water,  but  if  the  solution  be  diluted,  a 
white  powder  is  precipitated,  called  powder  of  algoroth.  It  is  an  oxy- 
chloride,  SbCl3,2Sb03  -f-  HO. 

488.  Sulphides  of  Antimony. — Two  sulphides  of  antimony  are  known, 
corresponding  in  composition  with  the  oxides  and  chlorides,  and  having 
the  formulae  SbS3,  and  SbS6.  The  first  of  these  is  the  native  sulphide  ;— 
when  this  is  roasted  in  the  air,  oxygen  is  absorbed,  and  oxysulphid 
of  antimony,  SbS3  -j-  Sb03,  is  formed,  often  called  glass  of  antimony,  or 
liver  of  antimony. 

When  the  native  sulphide  is  boiled  in  a  solution  of  potassa  or  soda,  a 
liquid  is  obtained,  from  which,  on  cooling,  an  orange-red  matter  is  de- 
posited, called  Kermes  mineral.  On  subsequently  neutralizing  the  cold 
solution  with  an  acid,  the  golden  sulphide  of  the  pharmacopoeia  is  ob- 
tained. These  compounds .  now  possess  little  interest,  but  formerly  were 
much  used  in  medicine. 

The  salts  of  antimony  are  unimportant,  except  tartar  emetic,  used  in 
medicine,  which  will  be  described  hereafter. 


BISMUTH. 

Symbol,  Bi;  Equivalent,  213 ;  Density,  9-8. 

469.  History,  Etc. — Metallic  bismuth  is  found  in  small  quan- 
tities in  Monroe,  Connecticut,  and  other  places,  but  is  chiefly 
obtained  from  the  native  sulphide.  In  mass,  it  much  resembles 
antimony  in  its  crystaline  structure,  but  has  «less  lustre,  and  is 
of  a  reddish  color.  It  is  brittle  when  cold,  but  may  be  ham- 
mered when  moderately  heated.  It  melts  at  about  477°,  and 
sublimes  at  a  high  temperature.  By  melting  a  considerable 
quantity  in  a  large  crucible,  placing  it  in  a  situation  to  cool 
very  slowly,  and  pouring  off  all  that  remains  liquid,  as  soon  as  it 
begins,  to  solidify  at  the  surface,  crystals  of  considerable  size  may 
be  obtained. 

The  metal  is  unchanged  in  the  atmosphere,  but  tarnishes 
slightly  by  moisture.  Heated  in  the  open  air  it  burns  with  a 
bluish  flame. 

It  is  too  brittle  for  use  by  itself  in  the  arts,  but  with  some  other  meta  9 

QUESTIONS. — 467.  What  is  said  of  the  chlorides  of  antimony  ?  468.  What 
sulphides  of  antimony  are  known  ?  469.  Is  bismuth  found  native  ?  De- 
scribe the  metal.  May  it  be  obtained  in  crystals  ?  What  is  said  of  its 
use  in  the  arts  ? 


368  LEAD. 

it  forms  important  alloys.     It  may  be  substituted,  in  whole  or  in  part,  for 
antimony  in  Britannia  metal  (4G5). 

In  some  of  their  chemical  properties,  antimony  and  bismuth  are  analo- 
gous to  phosphorus  and  arsenic,  and  also  to  nitrogen. 

Binary  and  other  Compounds  of  Bismuth. 

There  are  several  oxides,  chlorides,  &c. ;  but  they  possess  no  special 
iiterest. 

470.  Nitrate  of  Bismuth,  BiO,N05. — This  salt  is  formed  by  dissolving 
the  metal  in  nitric  acid.  It  is  soluble  in  water ;  but  if  the  solution  is 
largely  diluted,  the  salt  is  decomposed,  and  subnitrate  of  bismuth  precipi- 
tated. This  last  salt  is  used  in  medicine,  and  also  as  a  cosmetic. 


LEAD. 

Symbol,  Pb  (Plumbum);  Equivalent,  103-7;  Density,  1144. 

471.  History, — Lead  is  one  of  the  seven  metals  known  to  the 
ancients.     Its  most  important  and  most  abundant  ore,  from  which 
all  the  lead  of  commerce  is  extracted,  is  the  sulphide,  the  galena 
of  mineralogists ;  but  it  is  found  in  many  other  forms,  as  carbonate, 
sulphate,  phosphate,  &c.     It  is  very  abundant  in  different  parts 
of  this  country. 

472.  Preparation. — The  metal  is  reduced  from  the  native  sul- 
phide by  first  roasting  it  in  the  open  air,  and  subsequently  heating 
it  with  lime  in  a  charcoal  fire.     The  ore  usually  contains  a  little 
silver,  which  remains  in  combination  with  the  lead. 

The  metal  is  also  easily  reduced  by  heating  the  native  sulphide, 
in  fine  powder,  with  iron  nails,  in  a  close  crucible.  The  sulphur 
of  the  ore,  in  this  case,  passes  directly  to  the  iron,  forming  sul- 
phide of  iron. 

473.  Properties.  —  Lead   is   a  bluish-gray  metal,  and   when 
recently  cut  has  a  strong  metallic  lustre ;  but  the  surface  soon 
tarnishes  on  exposure  to  the  air.     It  is  soft  and  malleable,  but 

QUESTIONS. — 470.  Describe  the  nitrate  of  bismuth.  471.  What  is  the 
most  common  ore  of  lead  ?  What  other  ores  are  mentioned  ?  472.  How 
is  the  metal  reduced  from  the  native  sulphide  ?  What  is  the  fiiecond  modo 
mentioned  ?  473.  Describe  the  properties  of  lead. 


BINARY    COMPOUNDS     OF     LEAD.  369 

not  very  tenacious.  Heated  to  about  635°  it  melts,  and  at  very 
high  temperatures  is  slightly  volatilized.  Exposed  to  the  air  and 
moisture,  it  is  gradually  corroded ;  and  a  crust,  the  white  car- 
bonate, is  formed  upon  its  surface. 

The  peculiar  properties  of  lead  fit  it  for  use  in  the  arts  for 
many  purposes;  but  one  of  its  most  important  uses  is  in  con- 
structing pipes  for  conveying  water.  But  when  the  water  is  to 
be  used  for  drinking,  care  should  always  be  taken  to  have  the 
tubes  kept  constantly  filled  with  water,  as  the  introduction  of  air 
tends  to  form  the  highly  poisonous  carbonate ;  and  even  then  the 
water  should  not  be  used  until  it  has  been  proved  by  experiment 
that  the  particular  water  to  be  discharged  by  the  tube  is  not 
capable  of  acting  upon  the  lead. 

Lead  is  gradually  acted  .on  by  boiling  sulphuric  acid ;  but  its 
only  proper  solvent  among  mineral  acids  is  the  nitric,  which  forms 
with  it  a  soluble  salt. 

474.  Alloys  of  Lead. — Lead  forms  with  other  metals  many 
useful  alloys.  Two  parts  of  tin  and  one  of  lead,  fused  together, 
form  soft  solder,  which  is  much  used  in  cementing  together  the 
different  pieces  of  articles  made  of  tin-plate,  Britannia  metal,  &c. 
A  coarser  kind,  which  requires  a  higher  temperature  to  melt  it, 
is  composed  of  lead  3  parts  and  tin  1  part.  Pewter  is  an  alloy 
of  lead  and  antimony,  and  sometimes  a  little  copper.  '  Type- 
metal  is  an  alloy  of  3  parts  of  lead  to  1  of  antimony.  Tin,  lead, 
and  bismuth,  form  a  very  fusible  alloy  ;  when  made  of  8  parts 
of  bismuth,  5  of  lead,  and  3  of  tin,  it  will  melt  in  boiling  water. 

Binary  Compounds  of  Lead. 

475. 'Protoxide  of  Lead,  PbO. — Protoxide  of  lead  is  formed 
by  heating  lead,  in  the  open  air,  a  little  above  its  melting  point; 
oxygen  is  gradually  absorbed,  and  a  yellow  powder  formed,  which 
was  formerly  used  as  a  paint,  and  called  massicot.  As  usually 
manufactured,  it  is  in  the  form  of  reddish-yellow  scales,  occa- 

QUESTIONS. — What  is  said  of  the  use  of  lead  for  water-pipes  ?  What 
is  the  only  mineral  acid  that  dissolves  lead  ?  474.  What  alloys  of  lead 
are  mentioned?  What  is  pewter?  Type-metal?  What  alloy  of  lead 
melts  in  boiling  water  ?  475.  How  is  protoxide  of  lead  formed  ? 


370  SALTSOF    LEAD. 

sioned  by  its  having  been  partially  fused.  It  is  much  used  in 
painting  as  a  dryer,  and  is  called  litharge.  It  fuses  readily  at 
high  temperatures,  and  enters  into  combination  with  several  of 
the  earths  and  alkalies,  producing  a  transparent  glass,  which 
renders  it  an  excellent  substance  for  glazing  some  kinds  of 
earthenware.  With  powerful  bases  it  is  capable  of  combining 
as  an  acid. 

476.  Peroxide  of  Lead,  Pb02.  —  This  oxide  is  obtained  by 
digesting  red  lead  (the  compound  next  to  be  described)  in  nitric 
acid,  which  dissolves  out  the  protoxide,  leaving  the  peroxide  quite 
pure,  in  the  form  of  powder.     It  is  also  called  plumbic  acid. 

477.  Red  Oxide  of  Lead,  Pb3O4. — This  compound  is  the  red 
lead,  or  minium,  of  commerce,  much  used  in  the  arts  as  a  paint, 
and  as  one  of  the  ingredients  in  the  manufacture  of  flint  glass.  • 
It  is  formed  by  heating  metallic  lead  to  a  temperature  of  500°  or 
600°,  in  the  open  air,  so  as  to  oxydize  it  without  fusing  the  oxide, 
and  continuing  the  heat  for  some  time.     Heated  to  redness,  it 
gives  up  a  portion  of  its  oxygen  and  is  reduced  to  the  protoxide. 
Minium  is  a  compound  of  the  proto  and  peroxides  (2PbO,Pb02), 
and  is  therefore  a  plumbate  of  the  protoxide  of  lead. 

478.  Sulphide  of  Lead,  PbS. — This  compound  has  already  been  men- 
tioned as  constituting  the  only  important  ore  of  lead,  called  galena. 
It  is  also  formed  by  passing  a  current  of  sulphuretted  hydrogen  through 
a  solution  of  any  salt  of  lead.     As  it  occurs  native,  its  color  very  much 
resembles  that  of  metallic  lead,  and  its  structure  is  always  crystaliue. 

Salts  of  Lead. 

479.  Carbonate  of  Lead,  PbO,C02.—  This  is  the  white  lead 
of  commerce,  so  extensively  used  in  painting.     It  is  formed  by 
several  different  modes,  and  is  also  found  as  a  natural  production. 
Nearly  all  the  white  lead  of  commerce,  at  the  present  time,  is 
adulterated  by  mixing  sulphate  of  baryta  (399)  with  it  in  fine 
powder.     By  treating  the  mixture  with  nitric  acid,  the  carbonate 

QUESTIONS. — What  use  is  made  of  the  protoxide  of  lead  ?  What  is  said 
of  its  fusibility?  476.  Describe  the  mode  of  preparing  the  peroxide. 
477.  What  is  the  red  lead  or  minium  of  commerce?  What  use  is  made 
of  it?  478.  Describe  sulphide  of  lead.  479.  What  is  the  white  lesul 
used  by  painters  ?  With  what  is  it  usually  adulterated  ?  How  may  the 
fraud  be  detected  ? 


COPPER.  371 

of  lead  will  be  dissolved,  and  the  baryta  left  as  a  white  powder. 
Taken  into  the  system,  white  lead  acts  as  a  violent  poison,  pro- 
ducing the  disease  called  painters'  cholic. 

480.  Sulphate  of  Lead,  PbO,S03. — Sulphate  of  lead  is  found  native, 
and  called  anglesite  by  mineralogists.     It  is  also  formed  when  solution 
of  any  sulphate,  as  sulphate  of  soda,  is  mixed  with  solution  of  any  salt 
of  lead.     It  is  sometimes  used  in  painting  as  a  substitute  for  white  lead. 

Nitrate  of  Lead,  PbO,N05. — Nitrate  of  lead  is  easily  formed  by  dis- 
solving metallic  lead,  or  its  protoxide,  or  carbonate,  in  nitric  acid. 

Zinc,  iron,  and  tin  precipitate  lead  from  all  its  soluble  salts  in  its 
metallic  state.  Make  a  solution  of  1  part  of  nitrate  or  acetate  of  lead  in 
24  parts  of  distilled  water,  acidulated  with  acetic  acid,  and  suspend  in  it, 
near  the  top,  a  piece  of  clean  zinc ;  the  precipitation  of  the  lead  will 
immediately  commence,  and  in  the  course  of  24  or  48  hours,  the  metal 
will  appear  in  the  form  of  large  thin  leaves,  called  sometimes  arbor 
Saturni. 

481.  Test  of  Lead. — Hydrosulphuric  acid  precipitates  lead,  as  a  dark- 
colored  sulphide  from  all  its  soluble  salts,  and  even  blackens  those  that 
are  insoluble,  as  the  carbonate,  when  suspended  as  a  fine  powder  in 
water. 


COPPER. 

Symbol,  Cu  (^Cuprum)}  Equivalent,  31-7;  Density,  8-9. 

482.  History. — Copper  has  been  known  from  the  earliest  ages, 
and  is  often  found  in  the  earth  in  its  metallic  state.     Masses  of 
immense  size  of  nearly  pure  metal  have  been  found  in  the  region 
of  Lake  Superior.     One,  40  feet  long,  was  estimated  to  weigh 
200  tons.     It  is  also  found  as  a  carbonate,  sulphide,  and  oxide, 
as  well  as  in  other  combinations.     The  ores  of  copper  are  very 
generally  diffused,  some  of  them  being  found  in  almost  every 
country. 

483.  Preparation. — Metallic  copper  is  obtained  from  the  oxides 
and  the  native  carbonates,  simply  by  heating  these  ores  with  char- 
coal;   but  the  sulphide,   especially  when   mixed  with   iron,   is 

QUESTIONS.— -480.  What  is  said  of  the  sulphate  of  lead  ?  Describe  the 
mode  of  forming  the  arbor  Saturni.  481.  What  test  of  lead  when  in 
solution  is  mentioned?  482.  Has  copper  been  long  known?  What  is 
eaid  of  masses  that  have  been  found  native  ?  What  ores  of  copper  are 
mentioned  ?  483.  How  may  the  metal  be  reduced  from  its  oxf  des  and 
carbonates  ? 


372  BINARY    COMPOUNDS    OP    COPPER. 

reduced  with  more  difficulty,  and  the  process  is  too  complicated 
fco  be  given  here  in  detail. 

484.  Properties. — Copper  is  distinguished  by  its  peculiar  red 
color.     It  is  very  ductile  and  malleable,  but  less  tenacious  than 
iron.     To  fuse  it  a  bright  red  heat  is  required,  but  its  melting 
point  is  much  below  that  of  cast-iron.     It  forms  crystals  belong- 
ing to  the  monometric  system.     It  is  less  liable  to  be  corroded  by 
air  and  moisture  than  iron,  but  is  gradually  acted  on  by  the  joint 
agency  of  these  elements,  and  becomes  coated  with  a  green  crust, 
which  is  carbonate  of  copper.     Heated  to  redness  in  the  air,  it 
becomes  oxydized,  andjiitric  acid  readily  dissolves  it.     It  is  used 
extensively  in  the  arts,  both  alone  and  in  combination  with  other 
metals. 

485.  Alloys  of  Copper. — Copper  forms  with  other  metals  many 
very  useful  alloys.     Three  parts  of  copper  with  one  of  zinc  con- 
stitutes brass  ;   and  by  a  variation  of  the  proportions,  the  alloys 
called  tombac,  Dutch  gold,  and  pinchbeck,  are  produced.     Bronze 
is  an  alloy  of  copper  and  about  10  per  cent,  of  its  weight  of  tin ; 
and  bell-metal,  an  alloy  of  4  parts  of  copper  with  1  of  tin;  while 
speculum  metal,  used  for  the  mirrors  of  reflecting  telescopes,  con- 
tains about  2  parts  of  this  metal  to  1  of  tin.     Equal  parts  of  copper 
and  zinc  form  hard  solder,  which  is  used  in  soldering  articles 
of  brass. 

Binary  Compounds  of  Copper. 

486.  Oxides  of  Copper. — Red  oxide  of  copper,  Cu20,  is  a  sub- 
oxide  ;  it  is  found  native.     The  black  or  protoxide,  CuO,  is  also 
found  native,  and  is  produced  when  copper  is  heated  to  redness 
in  the  open  air.     It  is  also  easily  procured  by  heating  to  redness 
the  sulphate  or  nitrate  of  copper.     There  are  two  other  oxides. 

Chlorides  of  Copper. — Of  these  there  are  two,  the  subchloride,  Cu2Cl, 
and  the  protochloride,  CuCl,  but  they  possess  no  special  interest. 

Sulphides  of  Copper.- — There  are  two  sulphides  of  copper,  corresponding 
in  composition  to  the  chlorides,  viz.,  the  subsulphide,  Cu2S,  and  the  proto- 
sulphide,  CuS.  Copper  pyrites,,  vitreous  copper,  and  variegated  copper are 
native  sulphides  of  copper,  or  copper  and  iron. 

QUESTIONS. — 484.  How  is  copper  readily  distinguished  from  the  other 
metals  ?  Describe  its  properties.  485.  What  alloys  of  copper  are  used 
in  the  arts  ?  486.  What  oxides  of  copper  are  there  ?  What  chlorides  ? 
What  sulphides  ? 


SALTS    OP    COPPEE.  373 


Salts  of  Copper. 

487.  Sulphate  of  Copper,  CuO,S03,  or,  in  crystals,  CuO,S03 
-f  5HO. — This  is  the  blue  vitriol  of  commerce;  and  is  formed 
by  dissolving  the  protoxide  in  sulphuric  acid.     It  is  very  soluble 
in  water,  and  is  extensively  used  in  the  arts.     Its  color  is  a 
fme  blue. 

488.  Nitrate  of  Copper,  CuO,N06,  or,  in  crystals,  CuOjNOg  -f  3HO,  is 
easily  formed  by  dissolving  metallic  copper  in  dilute  nitric  acid.     It  does 
not  crystalize  readily;  and  is  deliquescent  in  the  air,  and  exceedingly 
corrosive.  * 

489.  Carbonates  of  Copper. — There  are  several  carbonates  of  copper, 
as  azurite  and  green  malachite,  which  are  found  native,  and  are  made  use 
of  as  ores  of  copper.     They  also  contain  water.     Green  verditer,  or  mineral 
green,  is  a  hydrated  subcarbonate,  obtained  by  precipitating  a  solution 
of  blue  vitriol  with  carbonate  of  potash  or  soda. 

Silicates  of  Copper,  more  or  less  hydrated,  are  found  native  in  the  mineraf 
species  called  dioplase  and  chrysocolla. 

490.  Arsenite  of  Copper,  or  ScKeele's  ffreen,  is  prepared  by  first  dissolving 
arsenious  acid  and  pearlash  together  in  warm  water,  and  then  pouring 
into  it  gradually  warm  solution  of   ;ulphate  of  copper.      It  is  of  a  beau- 
tiful green  color,  and  is  much  used  in  painting.     In  commerce,  it  is  called 
Paris  green. 

Test  of  Copper.  —  Ammonia  produces  a  deep  blue  color  in  diluted 
solutions  of  any  of  the  salts  of  copper,  by  which  they  may  always  be 
distinguished. 

491.  Vanadium,  V ;  Eq.,  68-6. — This  is  a  metal  of  rare  occurrence, 
being  found  only  in  some  iron  ores  in  Sweden,  some  lead  ores  in  Scot- 
land and  Mexico,  and  recently  in  some  copper  ores  from  Lake  Superior, 

Molybdenum,  Mo;  Eq.,  46. — Molybdenum  is  found  as  a  sulphide  IP. 
the  mineral  species  called  molybdenite,  and  also  in  other  combinations. 
It  is  a  white  metal,  and  has  a  density  of  8 '6." 

Tungsten,  W,  (Wolfram);  Eft.,  95.  —  This  metal  is  found  in  several 
mineral  species,  especially  the  "species  called  wolfram,  which  is  a  tung-  ' 
state  of  iron  and  manganese.     It  forms  several  oxides,  chlorides,  sul- 
phides, &c. 

Titanium,  Ti;  Eq.,  25. — Titanium  is  found  in  several  mineral  species, 
as  rutilc,  anatase,  and  brookite.  It  is  of  a  red  color,  and  resembles  cop- 

QUESTIONS. — 487.  What  is  the  commercial  name  for  sulphate  of  cop- 
per ?  488.  How  is  nitrate  of  copper  formed  ?  489.  What  is  said  of  the 
carbonates  of  copper  ?  490.  What  use  is  made  of  arsenite  of  copper  ? 
What  test  of  copper  is  mentioned?  491.  What  other  metals  are  men- 
tioned as  belonging  to  thisKgroup  ? 
32 


374  MERCURY. 

per.  Its  density  is  about  5-3.  The  native  oxide  is  used  m  coloring 
mineral  teeth,  so  as  to  imitate  the  color  of  natural  teeth. 

Uranium,  U;  Eq.,  60. — Uranium  occurs  in  several  species  as  pitch- 
blende, uranite,  &c.  Many  binary  compounds  of  it  are  known,  as  well  as 
some  of  its  salts. 

Columbium,  Cb,  is  the  name  given  to  a  metal  found  in  the  mineral 
species  called  columbite,  which  is  obtained  at  Middletown  and  Haddam, 
in  the  State  of  Connecticut. 

Tantalum,  Ta,  is  a  metal  very  similar  to  the  preceding,  which  is  ob- 
tained from  the  European  mineral,  tantalite.  Little  is  really  known  of 
these  two  metals*last  mentioned.  The  existence  of  the  two  metals  named 
pelopium  and  norium  (Table,  p.  145),  is  doubtful. 


MERCURY 

SILVER 

GOLD 

PLATINUM 

OSMIUM 

IRIDIUM 

PALLADIUM 

RHODIUM 


GROUP  VI. 


Noble  metals,  ivhose  oxides  are  reduced  by  a  red  heat. — No 
one  of  them,  except  osmium,  is  capable  of  decomposing 
water  under  any  circumstances. 

The  oxides  of  iridium  and  ruthenium,  and  some  of  those 
of  osmium,  are  not  perfectly  reduced  by  heat,  without  the 
presence  of  carbon,  or  some  deoxydizing  agent.  " 


RUTHENIUM  J 

MERCURY. 

Symbol,  Hg  (Hydrargyrum);  Equivalent,  100;  Density,  13-6. 

492.  History  and  Preparation. — Mercury,  or  quicksilver,  is 
on^  of  the  seven  metals  of  the  ancients.  It  is  sometimes  found 
in  its  metallic  state ;  but  most  of  the  mercury  of  commerce  is 
reduced  from  the  native  sulphide,  called  cinnabar.  It  is  not 
very  generally  diffused,  -there  being  but  few  mines  that  afford  it 
in  any  considerable  quantity.  Most  of  the  mercury  used  in  this 
country  comes  from  Spain  ',  but  it  is  obtained  also  in  Germany, 
Siberia,  in  Southern  Asia,  and  in  California. 

The  metal  is  extracted  from  the  native  sulphide  either  by 
roasting  it  alone,  so  as  to  oxydize  the  sulphur  and  sublime  the 
mercury';  or  by  heating  it  with  lime. 

QUESTIONS. — What  use  is  made  of  the  native  oxide  of  titanium  1  How 
are  the  metals  of  Group  VI.  characterized  ?  Name  the  metals  of  this 
group.  492.  Was  mercury  known  to  the  ancients  ?  By  what  other  name 
is  it  known  ?  From  what  ore  is  it  obtained  ?  What  is  the  mode  of  ex- 
tracting the  metal  from  the  native  sulphide  ?  *** 


MERCURY.  375 

Besides  the  native  compound  above  mentioned,  there  are  other  ores 
of  the  metal,  but  they  are  found  only  in  small  quantities. 

493.  Properties.  —  Mercury  is  distinguished  from  all  other 
metals  by  being  liquid  at  -ordinary  temperatures.     It  is  white  as 
silver,  and  has  a  brilliant  lustre.     Cooled  to  — 40°,  it  freezes  or 
becomes  solid,  and  is  then  very  malleable,  and  nearly  the  color 
of  lead  j  at  662°,  it  boils  and  forms  a  colorless  vapor,  the  density 
of  which  (air  being  1)  is  6-976.     At  lower  temperatures,  even  as 
low  as  70°,  it  gives  off  vapor,  as  is  shown  by  the  whitening  of 
pieces  of  gold-leaf  suspended  above  it  in  a  close  glass  bottle,  and 
by  its  action  upon  the  iodized  silver  plates  in  the  Daguerreotype 
process. 

The  best  method  to  obtain  solid  mercury  is  by  means  of  solidi- 
fied carbonic  acid  (58).  A  portion  of  the  solid  acid  is  made  in 
the  form  of  a  ball,  with  a  cavity  in  the  uppe*r  side  to  receive  the 
mercury,  and  the  whole  enveloped  in  cotton  to  protect  it  from  the 
atmosphere.  In  a  few  minutes  the  mercury  will  be  solid,  and 
may  be  preserved  in  this  condition  for  several  hours  with  a  very 
small  quantity  of -the  solid  acid.  The  metal  is  also  readily  frozen 
by  a  mixture  of  the  solid  acid  and  ether. 

.  By  slow  cooling,  mercury  forms  crystals   belonging   to  the 
monometric  system. 

494.  Mercury  is  usually  imported  into  this  country  in  strong  iron 
bottles,  and  generally  is  very  pure,  and  serves  for  every  purpose  without 
purification.     In  this  state  it  is  scarcely  oxydized  by  the  atmosphere, 
but  as  it  is  capable  of  dissolving  other*  metals,  as  tin,  lead,  silver,  and 
gold,  by  use  in  the  laboratory  it  often  becomes  contaminated  with  them, 
and  thus  is  more  liable  to  become  oxydized,  as  will  be  shown  by  a  pellicle 
of  oxide  floating  upon  its  surface.     In  this  state,  a  portion  will  adhere  to 
the  fingers,  or  other  substance,  when  dipped  in  it;  and  it' does  not  roll  in 
perfect  globules  over  the  surface  of  other  bodies,  like  pure  mercury. 

,  To  purify  mercury,  several  processes  are  resorted  to  ; — one  method  is 
to  pour  it  into  a  bottle  with  some  sulphuric,  acid,  or  dilute  nitric  acid, 
which  oxydizes  and  dissolves  the  foreign  metals.  It  should  stand  in  the 
bottle  several  days,  and  be  frequently  shaken  to  expose  all  the  metal  to 
the  action  of  the  acid.  At  the  proper  time,  the  mercury  is  to  be  removed 
and  washed  with  water. 

QUESTIONS. — 493.  Describe  the  properties  of  mercury.  Give  its  freez- 
ing and  boiling  points.  Does  it  evaporate  at  temperatures  below  its 
boiling  point  ?  How  may  it  be  solidified  ?  494.  What  other  metals  will 
mercury  dissolve  ?  How  may  it  be  known  when  other  metals  are  held  in 
Bolution  in  it?  Describe  the  method  of  purifying  mercury. 


376  MERCURY. 

Another  method  is  to  distil  the 
mercury,  by  which  it  is  separated 
perfectly  from  silver,  gold,  and  tin, 
but  not  from  arsenic,  zinc,  or  cad- 
mium, which  are  also  volatile.  To 
distil  mercury,  a  cast-iron  vessel  is 
used  of  the  form  represented  in  the 
figure.  When  using  it,  the  cover 
should  be  well  luted  on,  and  the 
tube  kept  cold  by  a  constant  stream 
of  cold  water. 

To   obtain   mercury   of    sufficient 

.^^^^^^^^^  purity  for  use  in  thermometers  and 

Distilling  Mercury.  %       barometers,  and  especially  the  latter, 

it  will  generally  be  found  necessary 

to  subject  it  to  both  of  these  modes  of  purification  in  succession,  the 
distillation  being  first  in  order. 

495,  The  only  acids  that  a'ct  on  mercury  are  the  sulphuric  and 
nitric  acids.     The  farmer  has  no  action  whatever  in  the  cold; 
but  on  the  application  of  heat,  the  mercury  is  oxydized  at  the 
expense  of  the  acid,  pure  sulphurous  acid  gas  is  disengaged,  and 
a  sulphate  of  mercury  is  generated.     Nitric  acid  acts  energetically 
upon  mercury,  both  with  and  without  the  aid  of  heat,  oxydizing 
and  dissolving  it  with  evolution  of  binoxide  of  nitrogen. 

496,  Uses, — Mercury  is  made  use  of  for  many  important  pur- 
poses, in  medicine,  in  the  laboratory,  and  in  the  arts.     In  the 
construction   of  thermometers  and    barometers   it   is  absolutely 
essential,  and  for  the  mercurial  bath,  to  enable  the  chemist  to 
collect  and  transfer  gases  that  are  absorbed  by  water.     In  union 
with  various  other  substances  it  constitutes  the  bases  of  many 
important   medicines.      Several   of  these   preparations   will   be 
described  in  their  proper  places. 

497,  Amalgams.  —  This  term  is  exclusively  applied  to  the 
alloys  of  mercury  with  the  other  metals. 

Quicksilver  unites  with  potassium  and  sodium  when  agitated 

in  a  glass  tube  with  that  metal,  forming  a  solid  amalgam.     When 

he  amalgam  is  put  into  water,  the  alkaline  metal  is  gradually 

QUESTIONS. — What  will  be  necessary,  in  order  to  obtain  mercury  of 
sufficient  purity  for  thermometers  and  barometers?  495.  What  acids 
only  act  upon  mercury  ?  Explain  the  action  of  sulphuric  acid.  Of  nitric 
acid.  496.  To  what  uses  is  mercury  applied?  497.  To  what  is  the 
name  amalgam  given  ? 


BINARY    COMPOUNDS    OP    MEROtFRY.  377 

wxydized,  hydrogen  gas  is  disengaged,  and  the  mercury  resumes 
its  liquid  form. 

A  solid  amalgam  of  tin  constitutes  the  silvering  of  looking- 
glasses  ;  and  an  amalgam  made  of  1  part  of  lead,  1  of  tin,  2  of 
bismuth,  and  4  of  mercury,  is  used  for  silvering*  the  inside 
of  hollow  glass  globes.  This  amalgam  is  solid  at  common  tem- 
peratures; but  it  is  fused  by  a  slight  degree  of  heat. 

The  amalgam  of  zinc  and  tin  (90)  is  used  for  promoting  the 
action  of  the  electrical  machine. . 


Binary  Compounds  of  Mercury. 

498.  There  are  two  oxides  of  mercury,  the  gray  oxide,  which 
is  considered  a  suboxide,  Hg20,  and  the  protoxide,  HgO,  which 
is  of  a  red  color.     The  suboxide,  Hg20,  is  readily  prepared  by 
mixing  calomel  briskly  in  a  mortar  with  pure  potassa  in  excess, 
so  as -to  effect  its  decomposition  as  rapidly  as  possible,  and  then 
washing  the  precipitate  formed  in  cold  water,  and  drying  sponta- 
neously in  a  dark  place.     This  oxide  is  a  black  powder,  and  is 
insoluble  in  water,  but  unites  with  the  acids  as  a  weak  base. 

The  protoxide,  HgO,  is  the  red  precipitate  used  in  medicine. 
It  is  formed  either  by  heating  mercury  nearly  to  its  boiling  point 
in  a  vessel  to  which  the  air  has  access,  or  by  cautiously  heating 
the  nitrate  so  as  to  expel  the  nitric  acid.  The  latter  mode  is  the 
one  usually  adopted.  It  is  usually  seen  in  very  small,  shining, 
crystaline  scales,  which  have  a  brick-red  color.  Heated  to  red- 
ness, it  is  decomposed,  yielding  mercury  in  the  gaseous  state,  and 
oxygen.  Red  oxide  of  mercury  is  slightly  soluble  in  water,  and 
gives  it  an  alkaline  reaction. 

499.  Subchloride  of  Mercury,  Hg2Cl;  eq.,  (200  +35-4=) 
235-4. — This  compound,  the  well-known  calomel  used  in  medi- 
cine, is  easily  prepared  by  pouring  a  solution  of  nitrate  of  the 
suboxide  of  mercury  into  a  dilute  solution  of  common  salt,  when 

QUESTIONS. — What  is  it  that  forms  the  silvering  of  mirrors  ?  498.  What 
oxides  of  mercury  are  there  ?  How  is  the  suboxide  prepared  ?  How  is 
the  protoxide  prepared  ?  What  is  it  called  ?  How  is  it  affected  when 
heated?  Is  it  soluble  in  water?  499.  What  is  calomel?  Describe  the 
mode  of  preparing  it.  To  what  use  is  it  applied  ? 
32* 


378     BINARY  COMPOUNDS  OF  MERCURY. 

the  calomel  is  precipitated  as  a  -white  powder,  which  is  insoluble 
in  water  and  the  acids  when  cold.  It  is  sometimes  found  native, 
and  is  called  horn-quicksilver,  or  native  calomel.  Its  density  is 
about  7. 

Calomel  is  sublimed  without  change  by  a  moderate  heat,  and 
may  be  obtained  in  small  crystals.  It  is  usually  seen  as  a  white 
powder,  with  a  slight  yellowish  tinge  j  and  may  always  be  knowr 
by  instantly  turning  black  as  ink,  when  touched  with  a  drop  of 
aqua  ammonite,  or  solution  of  any  caustic  alkali. 

This  compound  of  mercury  has  long  been  extensively  used  in  meelicine, 
and  the  estimation  in  which  it  has  been  held  may,  perhaps,  be  inferred 
from  the  names  by  which  it  has  been  known  at  different  times,  and  in 
different  countries.  The  following  are  some  of  them  :  —  Mercurius  dulcis, 
draco  miligalus,  sublimatum  dulce,  aquila  alba,  aquila  mitigata,  manna  metal-' 
lorum,  panchymogogurn  minerale,  panchymogogum  quercetanu's  ! 

Calomel  vapor  has  a  density  of  nearly  8-2,  and  is  composed  of  1  vol. 
of  mercury  vapor,  \  of  a  vol.  of  chlorine  condensed  to  1  vol.  Thus, 

1  vol.  of  mercury  vapor  weighs  6-976 
"       chlorine      *«  "       1.220 


1  vol.  subchloride  vapor  weighs  8-196 

500.  Chloride  of  Mercury,  HgCl;  eq.,  (100  +  354=)  135  4. 
—  Chloride  of  mercury  —  the  corrosive  sublimate  of  the  pharma- 
copoeia —  is  obtained  either  by  acting  on  mercury  by  nitrohydro- 
chloric  acid,  or  by  sublimation  from  a  mixture  of  sulphate  of  the 
protoxide  of  mercury,  and  common  salt.  The  latter  is  the  mode 
usually  adopted  in  practice.  Both  the  sulphate  and  the  salt 
should  be  perfectly  dry  and  well  mixed  ;  —  the  reactions  will  then 
be  as  follows  : 

HgO,S03  +  NaCl  =  NaO,S03  +  HgCl. 

The  sublimation  may  be  effected  in  a  retort  of  hard  glass  over 
a  charcoal  fire;  and  the  operation  should  be  conducted  in  such  a 
situation  that  all  the  fumes  escaping  may  be  immediately  con- 
veyed away  by  a  strong  draft  of  air. 

QUESTIONS.  —  May  'calomel  be  sublimed?  How  many  volumes  of  its 
constituents  does  one  volume  of  it  contain  ?  500.  How  is  chloride  of 
mercury  prepared  ?  By  what  name  is  it  known  in'pharmacy  ?  Describe 
the  reactions  wheel  sulphate  of  mercury  and  common  salt  arc  used  in  its 
preparation. 


BINARYCOMPOUNDS    OP    MERCURY.  879 

As  corrosive  sublimate  is  usually  seen,  it  is  colorless,  semi- 
transparent,  and  has  a  crystaline  structure.  It  has  an  acrid, 
burning  taste,  and  leaves  a  nauseous  metallic  flavor  on  the  tongue. 
It  has  a  density  of  6-5,  fuses  at  509°,  and  boils  at  563°.  It  is 
soluble  in  16  times  its  weight  of  water,  and  in  alcohol  and  ether. 
When  its  solution  in  water  is  agitated,  with  ether,  the  latter 
abstracts  the*  bichloride,  and  rises  with  it  to  the  surface  of  the 
former ;  and  it  may  thus  be  separated  from  many  other  substances 
when  contained  with  them  in  solution.  Its  aqueous  solution  is 
gradually  decomposed  by  light,  calomel  being  deposited. 

Applied  externally,  it  is  highly  corrosive  to  the  flesh;  and 
taken  internally  is  a  most  deadly  poison.  Albumen  precipitates 
it  as  an  inert  compound,  and  is  therefore  indicated  as  a  proper 
remedy  in  cases  of  poisoning  with  it. 

501.  The  kyanizing  (from  the  name  of  the  inventor,  Mr.  Kyan,)  of  tim- 
ber consists  in  soaking  it  for  a  time  in  a  solution  of  this  substance,  which 
protects  it  from  the  attacks  of  worins  and  insects ;  and  also,  by  combining 
with  the  albumen  contained  in  it,  preserves  it  from  decay. 

The  method  given  above  for  the  preparation  of  calomel,  though  very 
easy,  is  not  the  one  usually  adopted  in  practice;  a  better  result  is 
obtained  by  mixing  100  parts  (1  eq.)  of  mercury  and  135-4  parts  (1  eq.) 
of  corrosive  sublimate,  and  subliming  with  a  moderate  Ixeat,  the  whole 
being  converted  into  calomel.  Thus, 

Hg-f  HgCl  =  Hg2Cl. 

502.  Iodides  of  Mercury. — There  are  two  iodides  of  mercury,  corre- 
sponding in  composition  with  the  oxides  and  chlorides.     The  protiodide 
is  precipitated  as  a  beautiful  red  powder  by  mixing  together  solutions 
of  iodide  of  potassium  and  chloride,  of  mercury.      The  powder,   after 
washing  and  drying,  may  be  sublimed  by  a  moderate  heat,  but  it  then 
becomes  yellow.     After  cooling,  the  color  gradually  changes  to  red;  and 
the  change  is  instantaneous  if  it  is  rubbed  in  a  mortar. 

Its  vapor  has  the  highest  density  of  any  known  gaseous  substance, 
being  15-69.  It  appears  to  be  composed  of  equal  volumes  of  mercury 
vapor  and  iodine  vapor,  condensed  to  o»e  volume. 

1  vol.  iodine  vapor  weighs  8-716 
1    "    mercury  "          "        6-976 


1  vol.  vapor  of  HgLweighs  15-692 


QUESTIONS. — Describe  chloride  of  mercury.  Is  it  poisonous  ?  How  is 
a  solution  of  it  affected  by  albumen  ?  501.  In  what  does  the  kyanizing 
of  timber  consist?  Describe  the  mode  of  preparing  calomel  (or  sub- 
chloride)  by  using  the  chloride  and  metallic  mercury.  502.  What  iodides 
of  mercury  are  there  ?  Describe  the  protiodide,  and  the  mode  of  pre- 
paring it.  What  is  said  of  the  density  of  its  vapor  ?  Of  what  is  a  volume 
of  the  vapor  composed  ? 


380  SALTS    OP    MERCURY. 

503.  Sulphides  of  Mercury.  —  There  are  two  sulphides  of  mercury, 
•which  are  exactly  analogous  in  composition  to  the  preceding  compounds. 
The  protosulphide,  HgS,  as  we  have  seen,  constitutes  the  chief  ore  of 
mercury,  being  found  native,  as  cinnabar.  It  may  also  be  prepared  by 
art  in  several  ways,  and  then  forms  the  brilliant  red  pigment  called 
vermillion. 

In  vapor  the  density  of  this  substance  is  about  5-4  ;  and  1  volume  of  it 
•ontains  §  of  a  volume  of  mercury  vapor,  and  J  of  a  volume  of  sulphur 
vapor,  as  shown  below  : 

|-  vol.  mercury  vapor  weighs  (6-976  x  §  =)  4-651 
£  vol.  sulphur       «  «  ^^  —        0-739 


1  vol.  vapor  of  HgS  weighs  5-390 

As  §  -f-  -£  =  -§  -j-  a"  =  ¥'  ^  *s  evident  that  the  union  of  these  two  sub- 
stances is  accompanied  by  an  expansion  ;  —  it  is  the  only  instance  of  the 
kind  yet  known. 

The  other  binary  compounds  of  mercury  possess  no  special  interest. 


Salts  of  Mercury. 

504.  Nitrates  of  Mercury. — Nitric  acid  acts  violently  upon  mercury, 
and  forms  with  its  oxides  several  salts,  differing  from  each  other  accord- 
ing as  the  temperature  may  be  more  or  less  elevated,  or  the  acid  more  or 
le.=s  diluted.     Cold,  dilute  nitric  acid  acts  slowly  upon  mercury,  and  forms 
With  it  a  salt  of  the  suboxide,  which  crystalizes  with  two  atoms  of  water, 
and  has  for  its  formula  Hg20,N05-f2HO ;  but  if  the  acid  is  hot,  and  of 
the  usual  strength,  a  salt  of  the  protoxide  is  formed,  which,  when  crys- 
talized,  has  the  formula,  2HgO,N05  -f  2HO.     Still  other  nitrates  of  this 
metal  may  be  formed,  but  these  are  the  most  important. 

505.  Sulphates  of  Mercury.  — Sulphuric  acid  acts  but  slightly  upon 
mercury  when  cold;  but  if  healed,  a  sulphate  of  either  the  .suboxide  or 
protoxide  is  formed,  according  to  the  temperature.     If  5  parts  of  sul- 
phuric acid  are  boiled  upon  4  parts  of  mercury,  sulphate  of  the  protoxide, 
HgO,S03,  is  formed — the  compound  used  (500)  in  the  manufacture  of  cor- 
rosive sublimate.      Boiling  water  decomposes  this  sulphate,  forming  a 
yellow  basic  salt,  3HgO,S03,  called  turpetk  mineral. 

506.  Chlorosalts   of   Mercury.  —  Protochloride   of  mercury  combine- 
readily  with  other  metallic  chlorides,   forming  numerous  crystalizable 
sajts,  which  by  some  have  been  called  Ilydrar -go- chlorides.     Compounds 

QUESTIONS. — 503.  What  is  said  of  the  sulphides  of  mercury  ?  What  is 
vermillion 9  Of  what  is  one  volume  of  vapor  of  HgS  composed?  What 
is  said  of  the  union  of  these  two  substances  ?  504.  What  is  said  of  the 
nitrates  of  mercury  ?  505.  What  is  said  of  the  action  of  sulphuric  acid 
upon  mercury?  506.  Does  chloride  of  mercury  combine  with  other 
metallic  chlorides  ?  What  are  the  compounds  called  ? 


SILVER.  381 

of  this  character,  -with  the  chlorides  of  potassium,  sodium,  lithium,  am- 
monium, barium,  &c.,  are  made  simply  by  mixing  their  solutions.  The 
double  chloride  of  mercury  and  ammonium  was  formerly  used  in  medical 
practice,  under  the  name  of  salt  of  alembroth. 


'     .  SILVER. 

j 

Symbol,  Ag  (Argentum) ',  Equivalent,  108;  Density,  10'5. 

507,  History. — This  metal  was  known  to  the  ancients.      It 
frequently  occurs  native  in   silver  mines,  both  massive  and  in 
octahedral  or  cubic  crystals.     It  is  also  found  in  combination 
with  gold,  tellurium,    antimony,  copper,  arsenic,  •  and   sulphur. 
In  the  state  of  sulphide,  it  so  frequently  accompanies  galena,  the 
chief  ore  of  lead,  that  the  lead  of  commerce  is  rarely  quite  free 
from  traces  of  silver. 

Most  of  the  silver  mines,  which  afford  the  metal  at  the  present 
day,  are  in  South  America  and  Mexico ;  but  in  smaller  quantities 
it  is  obtained  in  several  countries  of  Europe,  and  other  parts  of 
the  world. 

NearJy  all  the  silver  obtained  from  the  mines  at  the  present 
time  is  found  native,  or  is  extracted  from  the  sulphide ;  but  there 
are  many  other  mineral  species  which  contain  the  metal. 

508.  Preparation. — When  metallic  silver  is  contained  in  small 
particles,  disseminated  through  the  ore,  it  is  extracted  by  tritu- 
rating the  ore  in  fine  powder  with  mercury,  which  dissolves  the 
silver,  and  separates  it  at  once  from  the  mass,  as  an  amalgam. 
The  amalgam  is  then  subjected  to  pressure  in  leather  bags,  by 
which  a  portion  of  the  mercury  is  separated,  and  tjie  remainder 
is  expelled  by  heat.     This  is  called  the  process  Qfjftmalgamation. 

Other  ores  of  silver  require  to  be  treated  differently,  but  the 
numerous  processes  adopted  cannot  be  here  described. 

Silver  is  purified  from  small  quantities  of  other  metals  present, 
except  gold,  by  the  process  of  cupellation,  which  has  been  prac 
tised  from  a  very  remote  age.  The  process  depends  upon  the 

QUESTIONS. — What  is  salt  of  alembroth?  507.  Has  silver  been  long 
known?  With  what  other  metals  is  it  found  associated?  From  what 
ores  is  most  of  the  silver  of  commerce  extracted?  508.  Describe  the 
mode  of  extracting  silver  from  its  ores  by  the  amalgamating  process. 


382  SILVER. 

fact  that  the  metals  (except  gold)  which  are  usually  in  combina- 
tion with  silver,  as  copper,  lead,  tin,  &c.,  are  more  oxidable  than 
silver,  and  therefore  when  the  alloy  is  kept  for  a  time  at  a  high 
temperature  in  the  open  air,  these  metals  are  oxydized,  and  the 
silver  left  perfectly  pure.  In  large  refineries,  the  oxide,  as  it  is 
formed,  is  blown  off  by  a  bellows,  so  as  to  expose  constantly  a 
fresh  surface  to  the  air)  but  in  small  opera- 
tions, as  in  the  testing  of  coin  or  plate,  the 
cupel  proper  is  used,  which  is  made  of  bone- 
earth,  of  the  form  of  a  small  cup,  as  represented 
Cupel<  in  the  figure.  This  has  the  peculiar  property 

of  absorbing  the  mixed  oxides  as  they  are  formed,  and  thus  the 
necessity  of  using  the  bellows  is  avoided.     For 
small  operations,  cupels  are  made  about  an  inch 
in  diameter,  and  half  an  inch  deep.     A  vertical 
Section  of  cupel.        section  is  shown  in  the  annexed  figure. 

509.  We  will  suppose  the  object  is  to  test  some  coin  or  plate, 
which  contains  with  the  silver  some  copper,  and  perhaps  a  little 
tin  or  lead.  A  small  piece  of  the  alloy  is  accurately  weighed, 
and  placed  in  the  cupel  with  10  or  20  times  its  weight  of  pure 
lead,  and  subjected  to  a  strong  heat,  in  such  a  manner  that  the 
air  shall  have  constant  access  to  it.  When  it  becomes  suffi- 
ciently heated,  oxydation  of  the  lead  and  other  metals  com- 
mences, and  the  mixed  oxides  being  absorbed  as  they  are  formed, 
after  a  little  time  the  silver  is  left  perfectly  pure.  The  cupel 
with  the  silver  is  then  removed,  and  when  cold  the  button  of 
silver  is  detached  and  again  carefully  weighed. 

The  heating  is  usually  conducted  in  a  muffle,  placed 
in  a  proper  furnace,  so  as  to  exclude  dust  and  smoke, 
but  allow  the  access  of  air.     The  muffle  (see  figure) 
Muffle  *s  *n  fa°t  a  small  oven,  made  of  fire-clay,  and  is 

placed  in  the  furnace  so  as  to  be  entirely  surrounded 
by  the  burning  fuel,  as  shown  in  the  figure  on  next  page,  which  repre- 
sents a  vertical  section  of  the  furnace  through  its  centre,  with  the  muffle 
in  its  place.  M  is  the  muffle,  with  several  cupels  in  it;  A,  B  and  C 
openings,  which  may  be  closed  at  pleasure  by  means  of  fire-brick  doors, 
A,  B,  C,  prepared  for  the  purpose.  To  insure  perfect  success  in  the. 

QUESTIONS. — 509.  Describe  the  process  of  cupellation.  Of  what  is  the 
cupel  formed  ?  What  purpose  does  it  serve  ?  Describe  the  muffle. 


SILVER. 


383 


operation,  attention  is  required  to  various 
particulars,  which  cannot  be  here  given  in 
detail. 

Alloys  of  gold,  subjected  to  the  same 
process,  are  purified  from  all  other  metals 
except  silver  and  platinum. 

510  Andther  mode  of  testing  alloys 
of  silver,  called  the  wet  method,  is  to 
dissolve  the  silver  alloy  in  nitric  acid, 
and  precipitate  the  silver  by  a  standard 
solution  of  common  salt,  previously  pre- 
pared with  accuracy.  This  solution  is 
made  of  such  a  strength,  that  1000  parts 
of  it,  by  measure,  will  precipitate  exactly 
1000  parts  by  weight  of  pure  silver ;  and 
the  proportion  of  silver  in  the  alloy  will 
of  course  be  determined  by  the  number 
of  parts  of  the  solution  required  to  pre- 
cipitate it.  This  is  the  mode  practised 
at  the  United  States  mints,  to  determine 
the  fineness  of  coin. 

This  method  cannot  be  .used  when  the 
alloy  contains  a  metal,  as  mercury,  whose 
chloride  is  insoluble. 


Section  of  Furnace  and  Muffle. 


511.  Properties. — Silver  is  a  soft,  white  metal,  and  is  very 
malleable  and  ductile.  It  has  a  brilliant  lustre,  and  is  susceptible 
of  receiving  a  very  fine  polish.  It  is  not  acted  upon  by  the 
atmosphere  or  by  moisture,  but  is  readily  blackened  by  sulphur. 
Articles  of -silver  often  become  tarnished,  merely  by  the  sulphurous 
gases  which  are  diffused  from  the  fires  in  houses  in  which  mineral 
coal  is  used  for  fuel. 

Its  melting  point  is  about  1873°,  and  if  kept  some  time  in 
fusion  it  absorbs  oxygen  in  large  quantity,  which  is  given  off  again 
when  the  metal  cools. 

Silver  is  attacked  by  sulphuric  acid  only  by  the  aid  of  heat, 
but  is  freely  dissolved  by  nitric  acid,  even  when  cold. 
•    Silver  is  used  in  every  country  for  many  important  purposes — 
for  coin,  and  for  manufacture  into  various  articles  of  utility  or 
ornament ;   but  to  render  it  more  stiff  and  hard  it  is  always 

alloyed  with  a  portion  of  copper. 

• 

QUESTIONS. — 510.  Describe  the  wet  method  of  testing  alloys  of  silver. 
611.  Describe  the  properties  of  silver.  What  acids  act  upon  it?  For 
what  purposes  is  silver  used  ? 


884  BINARY    COMPOUNDS    OF    SILVER. 

The  standard  of  purity  for  silver  coin  varies  in  different  countries; 
but  the  coin  of  the  United  States  contains  900  parts  of  pure  silver  and 
100  parts  of  capper ; — that  is,  one-tenth  part  of  the  -weight  of  the  coin  is 
copper,  except  the  three-cent  piece,  of  which  fths  are  silver  and  £th 
copper. 

At  the  present  time,  the  largest  silver  coin  issued  from  the  United 
States  Mint  is  the  half-dollar,  which  is  required  to  weigh  192  grains ; 
the  weight  of  the  smaller  coins  being  in  the  same  proportion,  except  that 
of  the  three-cent  piece,  which  is  12f  grains.  The  quantity  of  pure  silver 
in  the  half-dollar  is,  according  to  the  above,  172-8  grs.  =  192  — 19-2. 
This  gives  as  the  value  of  pure  silver  $1,38.8  per  ounce. 

The  value  of  coin  is  always  estimated  in  proportion  to  the  amount 
of  pure  metal  it  contains,  no  attention  being  paid  to  the  alloy.  It  is 
remarkable  that  the  addition  of  copper  scarcely  produces  any  change  in 
the  brilliant  white  color  of  silver,  provided  it  does  not  exceed  about  one- 
eighth  of  the  latter  metal. 

Silver  combines  with  other  metals,  forming  alloys,  which,  however, 
possess  no  particular  interest. 

Binary  Compounds  of  Silver. 

512.  Oxides  of  Silver. — Silver  forms  with  oxygen  three  compounds,  a 
suboxide,  Ag20,  protoxide,  AgO,  and  binoxide,  Ag02 ;  but  only  the  protoxide 
is  important.     This  is  thrown  down  as  a  dark-colored  powder,  when  solu- 
tion of  caustic  potash  is  poured  into  a  solution  of  nitrate  of  silver.    Heated 
to  redness  it  gives  up  all  its  oxygen,  and  pure  silver  is  obtained.     It  forms 
the  base  of  all  the  oxysalts  of  silver ; — is  slightly  soluble  in  water,  but 
very  soluble  in  aqua  ammonise. 

By  digesting  this  oxide  for  a  time  in  concentrated  aqua  ammonise,  a 
black  compound  is  formed,  which  is  highly  explosive,  sometimes  called 
fulminating  silver.  Its  composition  has  not  been  satisfactorily  determined. 
The  most  probable  opinion  is,  that  it  is  a  nitride  of  silver,  NAg3,  formed 
by  the  reaction : 

3 AgO  +  NH3  =  NAg3  4.  3HO. 

513.  Chloride  of  Silver,  AgCl;  eq.,  (108  -f  35-4=)  143-4.— This  com- 
pound is  occasionally  found  as  a  natural  production,  and  called  horn 
silver,  and  is  easily  formed  artificially,  by  pouring  solution  of  common 
salt  into  a  solution  of  nitrate  of  silver.     Formed  by  this  mode,  it  is  a 
beautiful  white  powder,  which,  however,  soon  becomes  purple  in  dif- 
fused light,  or  black  if  exposed  to  the  direct  light  of  the  sun,  or  if  warmed 
before  a  fire.      It  is  insoluble  in  water,  but  soluble  in  ammonia  and 
hyposulphurous  acid. 

QUESTIONS. — What  proportion  of  the  silver  coin  of  this  country  is  sil- 
ver? Wiat  is  the  alloy?  What  is  the  largest  silver  coin  now  issued 
from  the  "United  States. Mint?  What  does  this  give  as  the  value  per 
ounce  of  pure  silver  ?  In  estimating  the  value  of  coin,  is  any  allowance 
made  for  the  value  of  the  alloy  used?  512.  What  oxides  of  silver  are 
there?  Which  of  these  constitutes  the  base  of  the  salts  of  silver? 
613.  Describe  the.  chloride  of  silver.  How  is  it  prepared  artificially? 


SALTS    OF    SILVER.  385 

Nascent  hydrogen  reduces  it  to  the  metallic  state  by  absorbing  the 
chlorine  to  form  hydrochloric  acid.  To  effect  the  reduction,  the  chloride 
is  covered  with  water  acidulated  with  sulphuric  acid,  and  pieces  of  zinc 
introduced,  and  the  whole  occasionally  stirred.  The  metallic  silver  is 
obtained  in  fine  grains. 

Iodide  of  Silver,  Agl,  is  found  as  a  natural  production,  and  may  also 
be  formed  by  precipitation  from  solution  of  nitrate  of  silver  by  iodide 
of  potassium. 

Sulphide  of  Silver,  AgS. — This  compound  is  found  in  nature,  alone, 
and  in  combination  with  other  metallic  sulphides,  particularly  sulphide 
of  lead,  in  the  ore  called  argentiferous  galena.  Sulphide  of  silver  may  also 
be  formed  artificially  by  several  processes. 


Salts  of  Silver. 

614.  Nitrate  of  Silver,  AgO,N05.  —  This  is  the  only  salt  of 
silver  of  any  practical  importance,  and  is  well  known'  by  the 
name  of  lunar  caustic.  It  is  usually  sold  in  small  sticks,  which 
are  wrapped  in  paper,  but  may  also  be  obtained  in  beautiful 
white,  tubular  crystals.  The  sticks  usually  contain  a  portion  of 
nitre,  which  has  been  melted  with  it  when  cast  in  the  moulds. 
Nitrate  of  silver  is  formed  by  dissolving  silver  in  nitric  acid, 
diluted  with  twice  its  weight  of  distilled  water.  It  is  soluble  in 
one-half  its  weight  of  boiling  water,  and  its  own  weight  of  cold 
water.  It  is  the  basis  of  indelible  ink,  as  it  is  called;  but 
writing  done  with  it,  and  stains  made  by  it,  may  be  removed  by 
solution  of  cyanide  of  potassium.  Nitrate  of  silver  is  very  caustic 
to  the  flesh,  and  is  used  in  medicine  as  a  cautery.  From  its  solu- 
tion, metallic  copper  precipitates  the  silver  as  a  fine  powder;  by 
mercury,  the  silver  is  thrown  down  in  an  arborescent  form,  which 
has  been  called  the  arbor  Diance. 

Sttphate  of  Silver,  AgO,S03,  may  be  formed  by  boiling  sul- 
phuric acid  upon  metallic  silver.  It  is  a  colorless  salt,  slightly 
soluble  in  boiling  water. 

QUESTIONS. — Describe  the  mode  of  reducing  the  chloride  by  means 
of  zinc  and  oil  of  vitriol.     What  other  binary  compounds  of  silver  are 
mentioned?     514.    "What  is  lunar  caustic?     Describe  its  properties. 
What  use  is  made  of  it  ? 
33 


GOLD. 
GOLD. 

Symbol,  Au  (Aurum);  Equivalent,  198;  Density,  19-26. 

515.  History.  —  Gold  appears  to  have  been  known  to  the 
earliest  races  of  men,  and  to  have  been  esteemed  by  them  as 
much  as  by  the  moderns.  With  the  exception  of  the  rare 
mineral  telluride  of  gold,  it  has  hitherto  been  found  only  in  the 
metallic  state,  either  pure,  or  in  combination  with  other  metals. 
It  is  sometimes  found  in  quartzose  rocks,  but  more  frequently  in 
alluvial  depositions,  especially  among  sand  in  the  beds  of  rivers, 
having  been  washed  by  water  out  of  disintegrated  rocks  in  which 
it  originally  existed. 

Though  usually  found  in  irregular  rounded  lumps  and  grains, 
it  is  sometimes  obtained  in  crystals  of  the  monometric  system  as 


Crystals  of  Gold. 

« 

represented  by  the  accompanying  figures,  taken  from  the  American 
Journal  of  Science. 

Gold  is  obtained  at  the  present  day  in  large  quantities  in 
California,  Australia,  and  some  parts  of  the  Ural  Mountains, 
and  less  abundantly  in  Hungary,  and  other  countries  of  Europe. 
In  small  quantities,  it  occurs  in  Georgia,  North  Carolina,  and 
Virginia. 

516.  Preparation. — As  gold  exists  in  its  ores  in  the  metallic 
state,  it  is  generally  separated  from  them  by  the  process  of  amal- 

QUESTIONS. — 515.  Give  the  history  of  gold.  In  what  situations  is  it 
found?  Is  it  occasionally  found  in  crystals?  516.  Describe  the  mode 
•f  separating  silver  from  gold,  called  quartation. 


GOLD.  887 

Carnation,  similar  to  that  already  described  for  obtaining  silver, 
by  which  means  it  is  separated  from  all  other  metals  except  silver. 
To  remove  this,  so  much  silver  must  be  added  to  it  that  the  gold 
shall  constitute  but  a  fourth  of  the  whole,  and  the  mass  boiled  in 
nitric  acid,  which  then  readily  acts  upon  it,  dissolving  out  all  the 
silver,  and  leaving  the  gold  in  a  state  of  purity.  This  process 
has  been  called  quartatton,  from  the  circumstance  that  the  pro- 
portion of  gold,  in  order  that  the  nitric  acid  shall  dissolve  out  all 
the  silver,  must  not  exceed  a  quarter  of  the  whole  mass.  Other 
metals,  except  silver,  may  also  be  separated  from  it  by  cupel- 
lation  (508). 

To  prepare  absolutely  pure  gold,  a  piece  of  coin  may  be  dis- 
solved in  aqua  regia,  and  precipitated  with  soluti.on  of  sulphate 
of  protoxide  of  iron.  The  reactions  are  as  follows  : 

AuCl3  +  6FeO,S03  =  Au'+  Fe2Cl3  +  2(Fe203?3S03). 

The  gold  thus  obtained  is  in  a  minutely  divided  state,  and  is  of  a 
purplish  brown  color.  It  is  to  be  collected  on  a  filter,  and  washed 
with  very  dilute  hydrochloric  acid,  and  fused  with  a  little  borax 
and  saltpetre. 

517.  Properties. — Gold  is  readily  distinguished  from  all  other 
metals  by  its  brilliant  yellow  color,  and  by  its  great  malleability 
and  ductility.  It  is  capable  of  being  beaten  out  into  leaves  so 
thin  that  light  may  be  transmitted  through  them,  which  then 
»  appears  of  a  greenish  yellow  color.  It  is  not  acted  upon  by  air 
or  moisture,  though  exposed  to  their  influence  for  ages ;  nor  is  it 
oxydized  by  being  kept  in  a  state  of  fusion  for  any  length  of  time. 
When  intensely  heated  by  the  galvanic  current,  or  by  means  of  the 
compound  blowpipe,  it  burns  with  a  greenish  blue  flame,  and  is 
dissipated  in  the  form  of  a  purple  powder,  which  is  supposed  to 
be  an  oxide.  Selenic  acid,  aided  by  heat,  dissolves  it,  and  a 
mixture  of  selenic  and  hydrochloric  acids,  without  heat ;  but  its 
proper  solvent  is  aqua  regia,  which  is  a  mixture  of  1  part  of  nitric 
and  2  parts  of  hydrochloric  acid.  It  fuses  at  about  2016°. 

QUESTIONS. — Why  does  the  process  for  separating  silver  from  gold  here 
described  receive  the  name  quartaiion  ?  How  may  absolutely  pure  gold 
be  prepared?  »517.  How  is  gold  distinguished  from  the  other  metals? 
Describe  some  of  its  properties.  What  is  the  only  proper  solvent  of  gold  ? 


388  BINARY    COMPOUNDS    OF    GOLD. 

518.  Gold  and  silver,  from  the  estimation  in  which  they  have  been  held, 
have  been  long  known  as  the  "precious  metals;"  and  it  is  usual  to  esti- 
mate their  purity  in  carats.     A  carat  is  to  be  understood  as  J?th  part 
of  the  mass ;   and  a  piece  of  gold  or  silver  is  14,  18,  or  20  carats  fine, 
when  so  many  24ths  of  the  whole  are  fine  metal,  the  rest  being  alloy, 
But  in  the  Mint  of  the  United  States,  their  fineness  is  estimated  in  thou- 
sandths:  thus,  gold  or  silver  !s  said  to  be  "of  the  fineness  654,  789,  921, 
or  994  thousandths,  when  so  many  thousandths  of  the  whole  mass  con 
sist  of  pure  metal,  the  rest  being  alloy.     The  alloy  of  silver  is  always 
copper,  but  the  alloy  of  gold  may  be  either  copper  or  silver,  or  a  mixture 
of  the  two.     Pure  gold  is  so  soft  that  some  alloy  is  always  needed  to  give 
it  the  proper  stiffness,  and  to  prevent  too  rapid  wearing.     In  the  gold 
coins  of  this  country,  one-tenth  part  is  alloy,  which  is  a  mixtxire  of  silver 
and  copper.     The  gold  eagle  of  the  United  States  weighs  258  grains,  of 
which  25-8  grains  are  alloy.     The  value  of  standard  gold  is  therefore 
estimated  at  $18.604  per  ounce,  and  that  of  pure  gold  at  $20.671  per 
ounce. 

Native  gold  is  almost  always  alloyed  with  silver,  but  the  proportion 
of  this  metal  is  very  variable. 

Gilding  consists  in  coating  over  the  surfaces  of  bodies  with  a  thin  film 
of  gold.  Articles  made  of  metal  were  formerly  gilded  .by  applying  to 
their  surface,  properly  cleaned  and  smeared  with  nitrate  of  mercury, 
amalgam  of  gold,  and  then  expelling  the  mercury  by  heat ;  but  this  mode 
has  been  entirely  superseded  by  the  electrotype  process,  heretofore  (116) 
described.  In  both  cases  the  surface  of  gold  requires  to  be  burnished.  . 

Articles  made  of  non-metallic  substances  are  gilded  by  a-  coating  of 
gold  leaf. 

Binary  Compounds  of  Gold. 

519.  Oxides  of  Gold. — There  are  two,  and  perhaps  three,  oxides  of  gold ; 
but  the  teroxide,  Au03,  alone  possesses  any  special  importance.     It  is  of  a 
yellow  color  when  first  formed,  but  becomes  black  when  all  the  water  is 
expelled.     It  is  used  in  coloring  glass  and  porcelain  purple.     In  some 
cases  it  seems  to  act  the  part  of  a  feeble  acid,  and  has  been  called  ' 
auric  acid. 

520.  Chlorides  of  Gold. — There  are  two  chlorides  of  gold ;  the  terchloride, 
the  one  usually  seen,  is  formed  when  gold  is  dissolved  in  aqua  regia. 

By  evaporating  the  solution  carefully,  the  chloride  may  be  obtained  as  a 
solid,  which  is  very  soluble  in  water,  alcohol,  and  ether.  Solution  of 
chloride  of  gold  is  very  easily  decomposed  by  green  vitriol,  and  by  organic 

QUESTIONS. — 518.  Why  have  gold  and  silver  been  called  the  precious 
metals?  How  has  the  fineness  of  these  metals,  or  rather  alloys  of  them, 
usually  been  estimated  ?  What  is  meant  when  an  article  of  gold  or  silver 
is  said  to  be  18  carats  fine?  How  is  the  fineness  of  these  metals  esti- 
mated at  the  United  States  Mint  ?  What  is  the  alloy  used  for  the  gold 
coins  of  this  country  ?  What  is  the  weight  of  the  United  States  eagle  ? 
What  does  this  give  as  the  value  per  ounce  of  standard  gold  ?  Of  pure 
gold?  How  is  gilding  performed  ?  519.  What  oxides  of 'gold  are  there? 
620.  What  chlorides  ? 


PLATINUM.  389 

substances,     Protochloride  of  tin  forms  with  it  a  beautiful  purple  powder, 
called  purple  of  Cassius. 

Aqua  ammonia  precipitates,  from  solutions  of  terchloride  of  gold,  a 
fulminating  compound  called  fulminating  gold,  of  uncertain  composition. 

Salts  of  Gold. 

521.  The  oxides  of  gold  do  not  unite  as  bases  with  the  acids,  but  the 
teroxide,  as  an  acid,  combines  with  bases,  forming  some  unimportant 
salts,  which  are  called  aurates. 

Chlorosalts  of  Gold. — Terchloride  of  gold  combines  with  many  other 
metallic  chlorides,  like  the  chloride  of  mercury,  forming  a  series  of  chloro- 
salts, sometimes  called  auro-chlorides. 


PLATINUM. 

Symbol,  Pt;  Equivalent,  99;  Density,  21 '5. 

522.  History,  —  Platinum  was  first  recognised  as  a  distinct 
metal    in    1741,   but  was   not  described   until    1749.      It   has 
hitherto     been     obtained     chiefly     from 

Brazil,  Peru,  and  some  other  parts  of 
South  America,  and  from  the  Ural 
Mountains.  It  occurs  only  in  the  me- 
tallic state,  associated  with  other  metals, 
as  gold,  silver,  lead,  palladium,  osmium, 
iridium,  and  rhodium. 

523.  Preparation.  —  To  prepare  pure 
platinum,    the    native    grains,    or   com- 
mercial platinum,  are  dissolved  in  boiling 
aqua  regia,  and,  after  standing  for  a  time, 
the  clear  solution  is  poured  off,  and  the 
platinum  precipitated  by  solution  of  sal- 
ammoniac,  as  a  double  chloride  of  plati- 
num and  ammonium.     By  heating  this 
precipitate,   both    the  chlorine  and  am- 
monia  are    expelled,    and    the    metallic 

QUESTIONS.— How  is  purple  of  Cassius  formed?  521.  What  is  said 
of  the  chlorosalts  of  gold  ?  522.  Give  the  history  of  platinum.  What  is 
the  state  in  which  it  occurs  ?  523.  Describe  the  mode  of  preparing  pure 
platinum. 


390  PLATINUM. 

platinum  remains  as  platinum  sponge,  which,  when  treated  with 
hot  water,  appears  as  a  dark  gray  mud. 

This  is  now  pressed  in  a  hollow  cylinder,  by  which  means  the 
particles  of  metal  are  made  to  adhere,  so  that  the  disc  thus 
obtained  may  be  carefully  heated,  and  hammered  on  an  anvil. 
The  metallic  grains  now  become  firmly  welded  together,  and  the 
mass  may  be  worked  in  any  desired  form. 

524.  Properties, — Platinum  is  a  white  metal,  much  resembling 
silver,  but  of  a  darker  color,  and  of  inferior  lustre.  When  pure, 
it  is  very  malleable  and  ductile.  It  is  the  most  dense  substance 
known  to  man  (except,  perhaps,  iridium),  but  is  quite  soft;  and 
pieces  of  it,  when  heated,  may  be  welded  like  iron,  though  not 
so  easily.  No  single  acid  attacks  it,  but  it  is  soluble  in  heated 
aqua  regia.  By  heated  nitre,  or  potassa,  or  soda,  it  is  oxydized. 
It  cannot  be  melted  by  the  most  intense  heat  of  the  hottest  fur- 
nace ;  but  may  be  fused  by  the  compound  blowpipe.  When  a 
large  surface  of  the  metal  is  exposed  to  a  mixture  of  oxygen  and 
hydrogen,  it  has  the  singular  property  of  causing  them  to  com- 
bine, either  silently  or  by  an  explosion.  It  acts  in  this  way  more 
readily  when  used  in  the  spongy  form  (200,  523),  as  precipitated 
from  its  solution  by  sal-ammoniac. 

Platinum  black,  in  which  the  metal  is  in  a  still  more  finely 
divided  state,  acts  energetically  in  the  same  manner,  causing  the 
rapid  union  of  various  gases  besides  oxygen  and  hydrogen,  when 
submitted  to  its  influence.  This  form  of  platinum 
is  prepared  by  electrolizing  a  dilute  solution  of 
chloride  of  the  metal,  or  by  boiling  a  solution 
of  the  chloride  mixed  with  carbonate  of  soda  and 
sugar. 

If  a  coil  of  platinum  wire,  recently  ignited,  be  sus- 
pended in  a  deep  glass,  containing  a  little  ether  at  the 
bottom,  it  will  instantly  become  incandescent,  and  glow 

Wire  of  Plati-  >vith  a  red  heat'  uutil  the  etlier  is  entirely  dissipated. 
nam  over  Ether.  The  same  effect  may  be  produced  by  placing  a  coil  of 

QUESTIONS. — How  are  the  particles  of  finely  divided  metal  made  to 
unite  so  as  to  form  a  solid  mass  ?  524.  Describe  the  properties  of  plati- 
num. By  what  alone  is  it  dissolved  ?  How  is  it  affected  by  heated  nitre 
or  potash  ?  How  is  a  mixture  of  oxygen  and  hydrogen  affected  when 
exposed  to  a  large  surface  of  this  metal  ?  What  is  said  of  platinum  black 
in  this  connection?  Describe  the  experiment  with  a  coil  of  platinum 
wire  and  ether. 


BINARY    COMPOUNDS    OF    PLATINUM.          391 

small  platinum  wire  over  the  wick  of  a  spirit-lamp, 
and  after  lighting  it,  suddenly  extinguishing  the  flame. 
The  wire  will  continue  at  a  red  heat  until  all  the 
alcohol  is  consumed.  Such  a  lamp  (called  a  flamelcss 
'lamp)  is  represented  in  the  accompanying  figure. 

525.  Uses. — Platinum  is  of  great  importance 
in  the  laboratory,  and  is  much  used  in  the  arts, 
especially  for  retorts  for  condensing  (261)  sul- 
phuric acid.     Its  present  value  in  the  market  is 
about  half  that  of  gold.     It  was  formerly  issued 

AS  coin  by  the  Russian  government,  but  the  practice  has  been 
discontinued. 

Binary  Compounds  of  Platinum. 

526.  Oxides  of  Platinum. — Platinum  forms  with  oxygen  two  compounds, 
the  protoxide,  PtO,  and  the  peroxide,  Pt02,  both  of  which  are  feeble  bases, 
and  unite  with  some  of  the  acids  to  form  salts. 

Chlorides  of  Platinum. — Two  chlorides  of  platinum  are  known,  analo- 
gous in  coinposition^o  the  oxides.  The  bichloride,  PtCl2,  is  the  most 
important  of  all  the  impounds,  of  this  metal,  and  is  obtained  by  treating 
the  metal  with  boiling  aqua  regia,  and  carefully  evaporating,  to  expel  the 
excess  of  acid.  It  is  much  used  in  the  laboratory. 

Sulphide  of  Platinum,  PtS,  may  be  formed  by  heating  platinum-filings 
in  vapor  of  sulphur. 

527.  Salts  of  Platinum. — The  salts  of  platinum,  at  least  the  oxysalts, 
are  not  important.     Oxalate  of  the  protoxide,  and  sulphate  and  nitrate 
of  the  binoxide,  are  known. 

Chlorosalts  of  Platinum. — The  bichloride  of  platinum  combines  with 
other  metallic  chlorides,  forming  a  series  of  chlorosalts,  called  also 
platino-chlorides. 

528.  Osmium,  Os;  Eq.,  99-5. — This  rare  metal  is  in  combination  with 
platinum  arid  iridium  ; — with  the  former  in  the  so  called  native  platinum 
grains,  and  with  the  latter  in  the  mineral  species  called  iridosmine.    It  is  of  a 
grayish  oolor,  and  metallic  lustre ;  is  slightly  malleable,  and  has  a  density 
of  about  10.      It  combines  readily  with  oxygen   when  heated,  and  is 
attacked  by  nitric  acid,  which  converts  it  into  osmic  acid. 

Small  grains  of  the  native  iridosmine  are  used  for  the  tips  of  gold 
pens,  because  of  their  hardness  and  capability  to  resist  the  corrosive 
action  of  the  ink. 

QUESTIONS.  —  Describe  the  flameless  lamp.  525.  To  what  uses  is 
platinum  applied?  526.  What  oxides  of  platinum  are  known?  What 
chlorides  ?  How  may  sulphide  of  platinum  be  formed  ?  527.  Are  there 
any  important  salts  of  platinum  ?  528.  What  is  said  of  osmium  ?  What 
use  is  made  of  the  native  grains  of  osmium  and  iridium  ? 


392          BINARY    COMPOUNDS     OF    PLATINUM. 

There  are  known  no  less  than  five  oxides  of  osmium,  viz.,  OsO,  Os203, 
Os02,  Os03,  and  Os04 ;  of  which  the  last  two  possess  acid  properties,  and 
are  called  the  osmious  and  osmic  acids. 

Two  chlorides  only  of  osmium  are  known,  a protochloride  and  a  bichloride. 

529.  Iriditiin,  Ir;  Eq.,  99. — Iridium,  as  stated  above,  is  found  chiefly 
in  combination  with  osmium*     It  has  not  been  obtained  in  a  malleable 
state,  but  only  as  a  hard  compact  mass;  and  its  density  cannot  therefore 
be  well  determined,  but  by  some  it  is  believed  to  exceed  that  of  platinum. 
It  is  not  attacked  by  nitric  acid,  nor  even  by  aqua  regia  when  pure,  but 
at  a  red  heat  enters  into  combination  with  chlorine,  with  which  it  forma 
two  compounds,  the  protochloride,  IrCl,  and  the  bichloride,  IrCI2. 

530.  Palladium,  Pd;  Eq.,  53-3. — This  metal,  often  contained  in  plati- 
num ores,  is  obtained  chiefly  from  a  native  compound  of  this  metal  with 
gold,  found  in  some  parts  of  South  America.     It  is  nearly  as  white  as 
silver,  and  scarcely  less  fusible  than  platinum.    It  is  malleable  and  ductile, 
and  receives  a  fine  polish  under  the  burnisher.     Its  density  is  11-8. 

Palladium  is  used  for  the  construction  of  the  beams  for  delicate  balances, 
and  also  for  the  graduated  scales  of  astronomical  instruments. 

531.  Bhodium,  Rh ;  Eq.,  52-2. — Rhodium,  which  receives  its  name  from 
the  rose-color  of  some  of  its  compounds,  is  contained  in  small  quantities 
in  most  platinum  ores,  and  is  sometimes  found  in  cflfcibination  with  gold. 
It  is  of  a  gray  color,  and  even  more  infusible  than  platinum.     It  is 
attacked  by  aqua  regia  only  when  alloyed  with  platinum,  or  some  other 
metal.     Its  density  is  10-6. 

Kuthenium,  Ru,  is  the  name  given  to  a  metal  recently  discovered  in 
some  platinum  ores.  In  its  general  properties  it  resembles  iridium. 

QUESTIONS. — What  oxides  of  osmium  are  known?  529.  In  what  is 
iridium  found?  530.  Describe  palladium.  What  use  is  made  of  it? 
531.  Describe  rhodium.  What  is  said  of  ruthenium  ? 


PART  IV. 

SPECIAL    CHEMISTRY  — ORttANIO. 


GENERAL  PROPERTIES  OP  ORGANIC  BODIES. 

532,  Introduction. — In  the  preceding  part  of  this  work,  we 
have  traced  the  chemical  history  of  all  the  elementary  substances 
at  present  known,  and  that  of  many  of  their  most  important  com- 
pounds, as  they  are  produced  by  the  action  of  their  affinities, 
uncontrolled  except  by  the  agencies  of  heat,  light,  and  electricity; 
but  we  have  now  to  discuss  altogether  another  class  of  compounds, 
called  organic,  because  produced  almost  exclusively  by  the  organs 
of  plants  and  animals,  or  derived  from  substances  so  produced. 

Organic  Chemistry,  therefore,  is  that  branch  of  the  general 
science  of  Chemistry  which  treats  of  the  history,  properties,  and 
transformations  of  animal  and  vegetable  substances. 

These  are  always  compound,  and  differ  from  inorganic  or 
mineral  compounds  chiefly  in  their  origin,  and  in  the  circum- 
stance that  most  of  them  are  of  a  more  complex  composition. 

533.  Organic  and  Organized  Bodies.— There  is,  however,  a 
certain  class  of  organic  bodies, — called  organized  bodies, — whoso 
essential  physical  properties  are  altogether  peculiar.     These  are 
always  insoluble,  and  incapable  of  crystalization,  and  exhibit  an 
organized  structure,  often  visible  to  the  naked  eye,  and  always 
apparent  under  the  microscope.     To  this  class  belong  all  the 
proper  tissues  of  the  animal  and  vegetable  systems,  constituting 
the  organs  by  which  all  their  various  functions  are  performed. 
Sugar,  gum,  alcohol,  and  urea  are  organic  substances,  the  twc 

QUESTIONS. — 532.  What  has  been  treated  of  in  the  preceding  parts 
of  this  work?  What  are  now  to  be  treated  of?  Define  Organic  Chem- 
istry. How  do  organic  bodies  diifer  from  inorganic  ?  533.  What  are 
organized  bodies?  What  is  said  of  sugar,  gum,  £c  ? 

(393) 


394 


GENERAL    PROPERTIES 


former  being  found  ready  formed  in  plants  and  sometimes  in 
animals,  and  the  two  latter,  being  derived  usually  from  sub- 
stances so  produced,  but  they 
are  not  organized.  On  the 
other  hand,  the  cellular  tissue 
of  wood,  the  pith  of  an  elder 
tree,  and  the  skin  of  an  animal, 
are  organized;  and  their  pecu- 
liar structure  is  apparent  to  the 
eye,  at  least  when  aided  by  the 
microscope.  The  figure  in  the 
margin,  from  Regnault's  Chem- 
istry, represents  a  cross  section 
of  the  pith  of  the  elder,  as  seen 
under  the  microscope.  This  ex- 
hibits a  peculiar  regularity  of  structure,  which,  however,  is  not 
common ; — the  structure  of  two  different  organized  bodies  seldom 
presents  any  striking  similarity.  Of 
the  next  two  figures,  the  first  repre- 
sents a  microscopic  .view  of  a  longi- 


Pith  of  Elder. 


Stalk  of  Asparagus. 


Cross  Section  of  Same. 


tudinal  section  of  a  stalk  of  asparagus,  and  the  second  a  cross 
section  of  the  same. 

534,  Vitality. — In  the  production  of  organic  bodies,  the  simple 
affinities  of  the  particles  of  which  they  are  composed  are  over- 

QUESTIONS. — What  is  said  of  the  various  tissues  of  the  system  ?  How 
may  the  organized  structure  always  be  seen?  What  is  represented  by 
the  figure  in  the  margin?  What  by  the  next  two  figures?  534.  By 
what  are  the  affinities  of  matter  controlled  in  the  production  of  organic 
eompounds  ? 


OF    ORGANIC    BODIES.  395 

ruled  or  controlled  by  another  power  or  force,  called  the  vitat 
power,  vitality,  or  the  principle  of  life.  Its  influence  is  abso- 
lutely essential  for  the  production  of  most  organic  compounds, 
which,  it  is  believed,  can  never  be  formed  by  the  simple  opera- 
tion of  the  ordinary  affinities  of  the  elements  of  these  compounds. 
And  it  follows,  as  a  necessary  consequence,  -that  after  death,  that 
is,  when  this  principle  has  ceased  its  influence,  and  the  simple 
affinities  of  the  elements  of  an  organic  compound  are  left  uncon- 
trolled, they  will  show  a  disposition  to  break  up,  and  re-arrange 
themselves  in  a  new  order.  In  this  way  the  old  compound  is 
destroyed,  and  perhaps  several  new  ones  formed;  or  the  simple 
elements  may  be  entirely  set  free.  This  is  what  is  termed  the 
spontaneous  decay,  or  putrefaction  of  a  substance.  Often  this 
process  is  affected  by  the  presence  of  the  atmosphere,  and  is 
always  much  influenced  by  the  temperature,  and  other  circum- 
stances. 

Although  many  organic  compounds  are  found,  as  such,  in  the  bodies 
of  plants  and  animals,  by  far  the  greater  number  are  produced  by  the 
actions  of  the  various  reagents,  as  the  acids,  alkalies,  and  salts,  either 
cold  or  aided  by  heat,  upon  these  compounds.  Thus,  sugar  and  starch 
occur  abundantly  in  plants,  but  from  them,  by  the  action  of  reagents,  a 
long  list  of  other  compounds  are  produced,  which  are  never  found  in  the 
plants  themselves.  Alcohol,  the  almost  innumerable  ethers,  and  many 
acids,  are  of  this  kind.  .  Some  compounds,  as  acetic  and  oxalic  acid,  are 
found  ready  formed  in  organic  bodies,  and  may  also  be  produced  by  the 
action  of  reagents  upon  other  organic  substances. 

But  it  is  not  to  be  understood  that  all  organic  substances  are  equally 
liable  to  decay;  some  of  them,  as  sugar,  wood,  and  gum,  of  vegetable 
origin,  and  gelatine,  of  animal  origin,  if  kept  dry,  may  be  preserved 
apparently  for  any  length  of  time. 

The  chief  elements  of  organic  bodies  are  carbon,  hydrogen,  oxygen, 
and  nitrogen,  which  are  combined  in  different  modes,  and  in  different 
proportions ;  but  besides  these  some  organic  substances  also  contain  sul- 
phur, phosphorus,  chlorine,  calcium,  potassium,  sodium,  magnesium, 
iron,  silicon,  &c. 

Some  few  organic  compounds  have  been  formed  artificially,  that  is, 
without  the  aid  of  the  vital  principle  ;  but  not  any  organized  body. 

QUESTIONS. — Is  the  influence  of  this  principle  of  vitality  essential  to 
the  production  of  organic  compounds  ?  Why,  after  death,  do  most 
organic  siibstances  spontaneously  decay  ?  Are  most  organic  compounds 
found  ready  formed  in  the  bodies  of  plants  and  animals  ?  What  is  said 
of  alcohol  and  the  ethers  ?  May  some  organic  bodies  be  preserved  for  a 
long  period  ?  What  are  the  chief  elements  of  organic  bodies  ? 


896 


GENERAL    PROPERTIES 


535.  Molecular  Structure  of  Compounds, — It  is  well  known 
that  two  compounds,  exactly  the  same  in  composition  (172),  often 
differ  very  considerably  in  their  properties.  This  difference  is 
believed  to  be  occasioned  by  differences  in  the  mode  of  arrange- 
ment of  the  particles  in  the  cpmpounds,  or,  in  other  words,  in 
their  molecular  structure.  In  general,  while  we  understand  well 
the  elements  of  many  compounds,  we  really  know  little  of  the 
mode  in  which  these  elements  are  grouped  together  in  any 
particular  case.  We  know,  for  instance,  that  the  equivalent 
of  sulphuric  acid,  S03,  contains  1  atom  of  sulphur  and  3  atoms 
of  oxygen,  but  we  cannot  say  whether  these  are  grouped  as 
S  +  30,  SO +  20,  or  S02-f  0,  for  these  three  modes  are  all  alike 
possible.  Here  it  would  seem  that  there  can  be  only  three  modes 
of  combination,  but  in  more  complex  compounds  the  number  of 
possible  modes  may  be  greatly  increased. 

This  supposed  difference  in  the  mode  of  combination  or  grouping  of  the 
atoms  of  a  compound,  may  be  represented  to  the  eye  by  means  of  a  dia- 
gram. Thus,  let  us  suppose  that  we  have  a  compound  of  two  simple 


Modes  of  Grouping. 

substances,  and  that  in  the  atom  of  the  compound  there  are  8  atoms 
of  each  of  the  elements ; — representing  the  particles  of  one  kind  of  mat- 
ter by  the  dark  squares,  and  the  other  by  the  light  ones,  the  four  figures 
show  as  many  independent  modes  of  grouping.  Now,  as  every  inde- 
pendent mode  of  grouping  of  the  particles  may  produce  a  new  substance, 
it  is  plain  that  we  may  thus  have  four  substances,  all  having  the  same 
ultimate  composition,  yet  possessing  properties  altogether  different. 

536,  Compound  Radicals  —  Nomenclature. — Compound  radi- 
cals are  chemical  compounds  which  are  capable  of  performing  the 
functions  of  simple  substances;  they  combine  with  elementary 
bodies  and  with  other  compounds  in  the  same  manner  as  simple 

QUESTIONS. — 535.  May  substances  having  the  same  composition  differ 
in  their  properties  ?  How  is  this  difference  believed  to  be  occasioned  ? 
What  is  said  of  sulphuric  acid  in  this  connection  ?  How  is  the  supposed 
difference  in  the  mode  of  grouping  among  the  atoms  of  a  compound  illus- 
trated by  the  figure  ?  536.  What  are  compound  radicals  ? 


OFORGANIC    BODIES.  397 

substances,  and  may  often  be  substituted  for  these  in  the  com- 
pounds of  which  they  form  a  part. 

One  of  the  best  known  of  these  compound  radicals  is  cyanogen, 
C2N  (316),  which,  as  is  shown  by  the  formula,  is  a  bicarbonide 
of  nitrogen.  This  group  of  atoms,  it  is  well  determined,  is  capable 
of  combining  with  the  metals  and  other  substances  in  the  same 
manner  as  oxygen,  chlorine,  sulphur,  &c.,  producing  compounds 
similar  to  the  oxides,  chlorides,  &c.,  which  are  called  cyanides. 
United  with  oxygen  it  forms  cyanic  acid,  with  hydrogen  it  forms 
hydrocyanic  acid,  &c.  So  through  a  long  series  of  other  com- 
pounds, this  group  of  atoms  is  found  everywhere  performing  the 
functions  of  a  simple  substance. 

Other  compound  radicals  which  have  been  determined,  are  m/thyle, 
C2H3;  ethyle,  C4H5;  bufyryle,  C6H7;  valyle,  C8H9;  amyle,  C10Hn,  &o. 
Still  other  compounds  of  the  same  character,  but  having  a  more  com- 
plex composition,  are  benzyle,  C]4H502;  cacodyle,  C4H6As;  stanmethyle, 
C4H5Sn ;  zincmethyle,  C2H3Zn ;  stibmethyle,  (C2H3)3Sb,  &c. 

537.  That  these  groups  of  atoms,  and  many  others,  do  enter,  as  such, 
into  composition  with  the  simple  substances,  and  with  each  other,  and 
are  capable  of  being  transferred  by  single  or  double  decomposition  from 
one  compound  to  another,  are  facts  too  well  established  to  be  contro- 
verted. All  those  mentioned  above,  except  perhaps  benzyle,  have  also 
been  obtained  in  a  separate  state ;  and  many  that  have  not  been  thus 
obtained  may,  with  grjat  probability,  be  assumed  as  having  a  real 
existence. 

Considering  the  existence  of  these  groups  denominated  compound 
radicals  as  fully  established,  it  will  be  seen  at  once  that  it  furnishes 
a  ready  mode  of  classifying  organic  compounds,  and  also  for  forming  for 
them  a  systematic  nomenclature.  Thus,  if  we  take  ethyle,  C4H5,  as  the 
basis  or  starting  point  of  a  series,  we  have  for  its  binary  compounds  the 
oxide,  chloride,  iodide,  sulphide,  &c. ;  and  for  salts  of  its  oxide,  the 
hyponitrite,  nitrate,  acetate,  &c.,  as  follows,  viz. : 

Binary  Compounds. 

1.  Ethyle C4H6. 

-  2.  Oxide  of  ethyle,  C4H60,  common  sulphuric  ether. 

3.  Chloride      "        C4H5C1,  hydrochloric  " 

4.  Iodide         "        C4H6I,  hydriodic  " 

5.  Sulphide     "        C4H6S,  hydrosulphuric 

Salts  of  Oxide  of  Ethyle. 
1    Nitrite  of  oxide  of  ethyle,  C4H50,N04,      hyponitrous  ether, 

2.  Nitrate         "  "       C6H50,N05,      nitric  " 

3.  Acetate        "  "       C4H60,C4H303,  acetic 

QUESTIONS. — What  compound  radicals  are  mentioned?     537.   Have 
many  of  these  groups  have  been  obtained  in  a  separate  state  ? 
34 


898  GENERAL    PROPERTIES 

The  foregoing  are  given  as  examples  only; — this  series  might  be 
extended  much  further,  and  many  other  series  might  be  introduced,  as 
the  methyle  series,  which  would  include  the  compounds  of  methyle,  C2HS, 
analogous  to  the  above,  the  acetyle  series,  the  cacodyle  series,  &c.  A 
nomenclature  of  organic  compounds  constructed  on  this  principle  has 
been  adopted  by  able  and  judicious  chemists ;  but  as  there  is  no  proof 
that  such  a  nomenclature  truly  represents  the  real  molecular  structure 
of  these  compounds,  we  do  not  make  use  of  it  in  this  work. 

538.  A  slight  examination  only  is  needed  to  show  that  most  organic 
eompounds  may  be  arranged  in  series  in  a  variety  of  ways,  each  new 
mode  requiring  or  supposing  a  new  molecular  arrangement.     1'hus  in 
the  compounds  represented  in  the  table-  above,  if  we  commence  with  ole- 
fiant  gas,  or  ethylene,  C4H4,  instead  of  ethyle,  C4H5,  then  we  may  con- 
sider the  latter,  C4H5  =  C4H4,H,  as  the  hydride  of  ethylene,  and  ether, 
C4H50  =  C4H4,HO,  as  hydrate  of  ethylene,  hydrochloric  ether,  C4H6C1=: 
C4H4,  HC1,  as  hydrochlorate  of  ethylene,  &c. 

<* 

539.  The  real  mode  in  which  the  particles  of  organic  compounds  are 
arranged  (535),  at  least  in  most  cases,  has  not  yet  been  satisfactorily 
determined ;  and  it  is  therefore  impossible,  in  the  present  state  of  our 
knowledge,  to  fix  upon  a  proper  systematic  nomenclature.     The  same 
may  also  be  said  of  the  formulae  used  to  represent  these  compounds.     A 
distinction  is  often  made  between  empirical  and  rational  formula),  the 
former  representing  the  composition  as  determined  by  ordinary  analysis, 
without  any  attempt  to  indicate  the  arrangement  of  the  particles ;  the 
latter,  on  the  other  hand,  representing  not  only  the  composition  of  the 
compound,   but   also  its   molecular  structure.      Thus,   the  composition 
of  acetic  acid,  as  determined  by  analysis,  is  C4H404 ;  but  when  this  acid 
combines  with  a  base  it  always  parts  with  one  equivalent  of  water  (or  its 
elements),   so  that  its  salts,   the  acetates,   have   the   general  formula, 
RO,C4H303.     This  would  seem  to  indicate  that  the  formula  for  the  acid 
should  be  written  C4H303,HO.     But  certain  considerations  have  led  us  to 
the  belief  that  in  anhydrous  acetic  acid,  C4H303,   1  equivalent  of  the 
oxygen  is  held  in  a  different  state  from  the  rest,  and  therefore  its  fornmla 
should  be  C4H302,0.     Adopting  these  views,  then,  while  it  is  admitted 
that  the  empirical  formula,   C4H404,  represents  correctly  the  elements 
of  acetic  acid,  its  rational  formula  will  be,  C4H302.0  -\-  HO.     In  other 
words,  it  is  a  compound  having  for  its  primary  radical,  acetyle,  C4H3,  and 
for  its  secondary  radical,  C4H302. — (Dr.  Gibbs'  Report,  p.  43.) 

540.  In  the  following  pages,  a  systematic  nomenclature,  according  to 
any  particular  theory,  is  not  attempted; — the  names  of  compounds 
adopted  are  those  in  general  use,  with  a  few  unimportant  modifications. 

;  QUESTIONS. — Why  is  not  the  nomenclature  of  the  compound  radical 
theory  made  use  of  in  this  work?  538.  May  most  of  the  organic  com- 
pounds be  arranged  in  series  in  a  variety  of  ways  ?  Give  the  illustration 
in  the  text.  539.  Has  the  real  molecular  structure  of  organic  compounds 
been  determined  ?  What  are  empirical,  and  what  rational  formulee  ?  Give 
the  illustration  by  reference  to  acetic  acid.  540.  What  is  said  of  the 
nomenclature  used  in  the  remaining  part  of  this  work  ? 


OF    ORGANIC    BODIES.  899 

In  many  cases,  compounds  are  named  from  some  one  of  the  natural  pro- 
ductions in  which  they  are  found,  as  malic  add  from  malum,  an  apple ; 
citric  acid,  from  citron,  a  lemon ;  valerianic  acid,  found  in  the  root  of  the 
plant  called  valeriana,  offidnalis ;  cinchonia,  obtained  from  the  bark  of  the 
cinrhonia  condaminea,  &c.  The  formulae,  in  general,  are  to  be  considered 
only  as  empirical ;  frequently,  two  formulae  are  given  for  the  same  com- 
pound, with  the  sign  =  between  them.  In  such  cases,  the  first  is  always 
the  empirical  formula,  while  the  second  indicates  something  further,  as  it 
regards  the  supposed  constitution  of  the  compound,  or  the  mode  of  its 
reactions  with  other  substances.  The  formula  for  cane  sugar,  for  in- 
stance, is  written  Cl2HnOn  —  Cl2H9Og-\- 2110,  by  which  it  is  indicated 
that  2  equivalents  of  water  (or  the  elements  of  water)  sustain  a  relation 
to  the  compound  different  from  that  of  the  other  atoms  of  these  elements. 


Laws  of  Combination  and  Transformation. 

541,  We  have  seen  (536),  that  in  organic  compounds  -certain 
groups  of  atoms,  called  compound  radicals,  frequently  are  found 
to  perform  the  functions  of  simple  substances.  Many  of  these 
groups  are  already  known,  and  many  more  will  probably  be  here- 
after discovered.  .  If  all  the  groups  capable  of  acting  in  this  man- 
ner, with  their  properties  and  relations,  were  known,  it  is  very 
probable  that  the  transformations  of  organic  bodies  would  not 
differ  essentially  from  those  of  inorganic  matter,  except  as  they 
are  affected  by  this  circumstance.  In  other  words,  all  cases 
of  chemical  action  would  be  reduced  to  instances  of  direct  union, 
or  of  single  or  double  elective  affinity. 

When  potassium  is  burned  in  oxygen  gas,  direct  union  takes  place 

between  the  two  elements,  and  potassa  (oxide  of  po'tassium)  is  formed 

K  -f-  0  =KO.  But  when  potassium  is  thrown  into  water,  we  have  a  case 
of  single  elective  affinity,  as  shown *by  the  equation  representing  the 
reaction ; — thus,  K  -j-  HO  =  KO  -f-  H.  We  may  say  in  this  case,  either 
that  the  oxygen  is  transferred  from  the  hydrogen  to  the  potassium,  or 
that  the  potassium  has  replaced  the  hydrogen  of  the  water.  When 
solutions  of  nitrate  of  baryta  and  sulphate  of  soda  are  mixed  together, 
we  have  an  instance  of  what  is  called  double  elective  affinity ;  and  by  a 
double  transfer  of  elements  we  have  formed  the  two  new  compounds,  sul- 
phate of  baryta  and  nitrate  of  soda.  Thus, 

BaO,N05  -f  NaO,S03  =  BaO,S03  -f  NaO,N05. 

QUESTIONS.- — How  are  compounds  often  named?  Are  the  formulae 
given  to  be  considered  as  empirical  or  rational?  541.  What  is  said 
of  the  transformations  of  organic  compounds  as  compared  with  thoso 
of  inorganic  matter?  What  illustrations  are  given  from  inorganic 
chemistry  ? 


400  GENERAL    PROPERTIES 

542.  So  in  organic  chemistry,  most  if  not  all  reactions  mil  be  similar 
to  one  or  another  of  the  above  cases.  When  olefiant  gas,  C4H4  (308), 
which  is  properly  an  organic  product,  and  chlorine,  Cl,  are  brought 
together,  they  combine  to  form  an  oil-like  liquid,  C4H4C12.  But  often 
when  two  compounds  have  in  this  way  combined,  the  new  and  more  com- 
plex compound  that  is  formed  may,  by  a  slight  change  of  circumstances, 
or  even  spontaneously,  break  up  into  compounds  of  less  complex  consti- 
.  tution.  We  have  a  case  of  this  kind  in  sulpho-vinic  acid,  which  is  formed 
by  the  union  of  alcohol,  C4H602,  with  sulphuric  acid.  Thus, 

C4H602+2(S03,HO)  =C4H6Oa,2(S03HO)  =  C4H60,HO,  2(S03HO). 

This  last  substance,  called  monohydrated  sulpho-vinic  acid,  when 
heated,  breaks  up,  not  into  alcohol  and  monohydrated  sulphuric  acid, 
but  into  ether,  C4H50,  and  2S03,3HO. 

But  most  of  the  transformations  in  organic  bodies  may  be  considered 
as  instances  of  double  decomposition,  or  double  elective  affinity.  The 
action  of  chlorine  upon  acetic  acid  is  properly  of  this  kind,  as  is  shown 
by  the  following  equation.  Thus, 

C4H404  -f  6C1  =  C4HC1304  +  3HC1.    , 


Acetic  Acid.     -  Cbloracetic  Acid. 


It  is,  indeed,  true  that  chlorine,  one  of  the  substances  used,  is  not  a  com 
pound,  but  we  are  to  consider  that  the  action  is  the  same  as  if  each  of 
the  three  atoms  of  hydrogen  were  successively  replaced,  giving  for  tha 
first  step  in  the  process  the  reaction,  C4H404  -f-  2C1  =  C4H3C104  -f  HC1. 
One  atom  of  the  chlorine  is  transferred  to  the  acetic  acid,  which  at  the 
same  time  gives  up  1  atom  of  its  hydrogen  to  combine  with  the  second 
atom  of  chlorine,  to  form  hydrochloric  acid.  This  reaction  three  times 
repeated  results  as  given  above,  in  the  replacement  of  3  atoms  of  hydrogen 
by  as  many  atoms  of  chlorine. 

543,  Substitution  or  Metalepsy. — We  have  seen  above  that 
by  the  action  of  chlorine  upon  acetic  acid,  C4H404,  the  latter  loses 
3  atoms  of  hydrogen,  and  takes  in  their  place  3  atoms  of  chlorine ; 
in  other  words,  3  atoms  of  chlorine  are  substituted  in  the  acid  for 
an  equal  number  of  atoms  of  hydrogen.  The  new  compound, 
C4HC1304,  is  called  chloracetic  acid,  and  in  most  of  its  properties 
closely  resembles  acetic  acid,  from  which  it  has  been  formed. 
Transformations  of  this  kind  are  of  very  frequent  occurrence; 

QUESTIONS. — 542.  What  is  the  effect  when  olefiant  gas  and  chlorine 
are  brought  together?  When  two  siibstances  combine  so  as  to  form 
a  more  complex  compound,  will  they  sometimes  break  up  in  such  a 
manner  as  to  form  compounds  different  from  those  which  at  first  united  ? 
Give  the  illustration  by  reference  to  alcohol  and  sulphuric  acid.  What 
is  said  of  acetic  acid  and  chlorine  in  this  connection  ?  543.  What  is  the 
change  produced  in  acetic  acid  by  the  action  of  chlorine  ? 


OF    ORGANIC    BODIES.  401 

and  the  exchange  or  substitution  may  take  place  between  atoms 
or  groups  of  atoms  (compound  radicals)  which  are  similar  to  each 
other  in  their  chemical  relations. 

Hydrogen  seems  to  be  more  frequently  replaced  than  any  other  element; 
and  there  may  be  substituted  for  it  chlorine,  iodine,  bromine,  or  a  metal, 
or  even  a  compound  radical, -as  methyle,  ethyle,  &c.  Instances  of  the 
latter  kind  are  seen  in  ethylamine,  diethylamine,  &c.,  in  which  one  or 
more  atoms  of  hydrogen  in  ammonia  are  replaced  by  ethyle.  Thus, 
ammonia  ==NHHH,  ethylamine  =  NHHC4H6,  dietnylamine  =  NH(C4H5) 
(C4II6)  =  NH(C4H6)2,  &c. 

As  hydrogen,  chlorine,  iodine,  &c.,  form  a  natural  family,  one  of  which 
may  replace  another  in  the  compounds  they  form ;  so  nitrogen,  phos- 
phorus, arsenic,  antimony,  and  bismuth  form  another  family,  the  indi- 
viduals of  which  ^sustain  a  similar  relation  to  each  other.  Arsenide 
of  hydrogen,  AsH3  (292),  corresponds  to  ammonia  in  which  the  nitrogen 
is  replaced  by  arsenic ;  and  the  compound,  Sb(C4H6)s,  may  be  regarded 
as  ammonia  in  which  the  nitrogen  is  replaced  by  antimony,  and  the 
hydrogen  by  ethyle. 

Still  another  natural  family  is  formed  by  oxygen,  sulphur,,  selenium, 
and  tellurium.  Alcohol,  C4II602,  by  a  substitution  of  sulphur  for  its 
oxygen,  forms  mercaptan,  or  sulphur  alcohol,  C4H6S2. 

544.  Conjugated  or  Coupled  Compounds. — Many  of  the  com- 
pounds produced  by  transformations  in  accordance  with  the  above 
principles," are  frequently  called  conjugated  or  coupled  compounds. 
They  may  be  radicals  only,  or  acids,  or  bases.      As  the  name 
implies,  they  are  supposed  to  be  formed  by  the  union  of  other 
compounds ;   and  usually  the  characteristic  properties  of  one  or 
the  other  of  the  coupling  compounds  will  be  more  or  less  pre- 
served in   the   new  or   coupled  compound.      Thus,  ethylamine, 
NHHC4H5,  is  a  coupled  or  conjugated  ammonia; — it  is  a  sub- 
stance formed  on  the  type  of  ammonia,  and  possessing  nearly  the 
same  properties,  ethyle,  C4H5,  being  the  couplet.     So  the  com- 
pounds, (C4H6)3Sb,  C4H5,Zn,  C2H3Bi,  &c.,  are  called  conjugate 
metals: 

545.  Homologous  Bodies.  —  Homologous  bodies   are   bodies 
which   may  be  arranged  in  series,  all  the   members   of  which 
are   similar  in  their  general  properties  and  chemical  relations, 

QUESTIONS.— Between  what  may  substitutions  take  place  ?  What  other 
elements  or  compound  radicals  may  be  substituted  for  hydrogen  ?  What 
elements  constitute  a  natural  family  with  nitrogen,  capable  of  replacing 
each  other?  544.  What  are  conjugated  or  coupled  compounds?  What 
examples  are  given  ?  545.  What  are  homologous  bodies  ? 
34* 


402  GENERAL    PROPERTIES 

and  are  composed  of  the  same  elements,  but  differ  from  each 
other  in^  composition  by  the  addition  or  subtraction  of  the  ele- 
ments, C2H2,  or  some  multiple  of  this  expression.  Of  this  kind 
are  the  alcohols,  all  of  which,  though  they  differ  greatly  in  some 
of  their  properties,  still  have  many  points  of  resemblance.  The 
composition  of  all  that  are  known  will  be  seen  by  the  following 
table  : 

Names.  Formulae. 

1.  Methylic  alcohol  (wood  spirit)  ..................  C2H4Oi 

2.  Common,  or  wine  alcohol  .........................  C4H602. 

3.  Propylic  alcohol  .....................................  C6H802. 

4.  Butyric         «      ..................................  „  C8H1002. 

5.  Amylic          "      (fusel  oil)  ........................  C10H,202. 

6.  Caprylic       "       ...................................  C,6IT1802. 

7.  Ethal  (ethalic  alcohol)  ............................  C32TT3402 

8.  Cerotine  (cerotic  alcohol)  .........................  C^II^O^ 

9.  Melissine  (melissic  alcohol)  .......................  C60H6202. 

Each  of  these  compounds,  denominated  alcohols,  it  will  be  seen,  con- 
tains 2  atoms  of  oxygen;  —  the  first,  or  methylic  alcohol,  contains  C2H4; 
the  second,  C4TT6  =  C2H4  -f  C2H2  ;  the  third,  C6H8,  and  so  on  for  the 
others,  by  the  addition  in  each  case  of  C2H2,  or  some  multiple  of  this 
expression.  In  the  crises  requiring  a  multiple  of  C2H2,  it  would  seem 
that  one  or  more  intermediate  compounds  are  wanting.  These  may  here- 
after be  supplied  ;  —  as,  for  instance,  between  amylic  and  caprylic  alcohol 
the  compound,  C,4H1602,  is  not  yet  known,  but  when  a  compound  having 
this  constitution  shall  be  discovered,  it  is  safe  to  predict  that  it  will  have 
the  general  properties  of  this  class  of  bodies. 

We  have,  therefore,  as  a  general  expressive  for  the  alcohols,  the 
formula,  C8BH2(B  +  ,)02. 

Besides  the  above  series  of  alcohols,  many  other  series  are  known, 
among  which  are  the  following,  taken  from  Gibbs'  Keport  : 

Hydrogens.  Acetenes.  Formic  Acids.  Oleic  Acids. 

H  C2II2  C2H204  C6H404 

C2H3  C4H4  C4H404  C8H604 

C4H6  C6H6  C6H604  CJOH804 

C6H7  C8H8  C8H804  C12H1004 

4  C2nH2(n_1)04 


546.  The  compound,  C2H2,  which  in  all  these  series  sustains  so  im- 
portant a  relation,  has  been  called  the  homologizing  body.  But  it  is 

QUESTIONS.  —  In  what  do  homologous  bodies  of  the  same  series  differ 
from  each  other  in  composition  ?  What  series  of  substances  of  thia 
kind  is  mentioned?  What  is  said  of  the  composition  of  the  alcohols? 
Give  the  general  formula  for  the  alcohols.  546.  What  is  the  compound, 
CtH8,  here  called? 


OP    O  R  a  A  N  1 0    BODIES.  403 

probable,  that  in  other  series  other  compounds,  or  perhaps  a  certain 
number  of  atoms  of  an  element,  may  serve  as  the  homologizing  body. 
Thus,  the  ethyle  and  phenyle  compounds  differ  from  each  other  by  Cg, 
which  may  be  considered  as  the  homologizing  body  connecting  the  cor 
responding  compounds  of  the  two  classes,  so  as  to  form  two  terms  of  a 
homologous  series. 

547.  Homologous  bodies  of  the  same  series  are  in  general  similarly 
affected  by  the  action  of  a  reagent ;   and  the  resulting  compounds  will 
be  homologous.     This  is  implied  in  the  definition  of  those  bodies  given 
above.      The   alcohols,   C^H^n-j-^O^   f°r   instance,   by  the   action   of 
oxydizing  reagents  yield  corresponding  homologous  acids,  C2;iH2n04 ; — 
and  intermediate  between  the  alcohol  and  acid,  in  several  cases,  another 
compound  is  known,  called  an  aldehyde  (from  alcohol  dehydrogenatus), 
and  having  the  composition,  C^H^Og.      Other  compounds  of  this  series, 
we  may  confidently  anticipate,  will  hereafter  be  discovered. 

The  following  table  contains  the  formulae  of  the  alcohols,  their  cor- 
responding aldehydes  (when  known),  and  acids: 

Alcohols.  Aldehydes.  Acids. 

1.  Methylic...  C2H402     C2H204. 

2.  Wine C4H602     C4H402       C4H404. 

3.  Propylic....  C6H802     C6H602       C6H604. 

4.  Butyric C8H1002  C8H802       C8H804. 

5.  Amylic C10H1202 C10H1002 

6.  Caprylic  . 

7.  Ethalic 

8.  Cerotic 

9.  Melissic.. 

Besides  the  acids  in  the  above  list,  several  others  are  known  of  the 
same  series,  some  of  which  will  hereafter  be  mentioned ;  but  the  cor- 
responding alcohols  and  aldehydes  have  not  been  discovered. 

548.  In  every  homologous  series  as  yet  known,  containing  oxygen,  the 
number  of  atoms  of  this  element  is  constant ;  and  the  same  appears  to  be 
true  of  nitrogen,  as  will  hereafter  be  shown. 

In  the  alcohol  series,  C2,,H2(n-f-j)02,  it  is  evident  the  smallest  value 
we  can  give  to  n  is  1,  and  the  formula  then  becomes  C2II402,  which 
represents  methylic  alcohol,  but  what  the  extreme  upper  limit  may  be 
we  are  ignorant.  If  in  the  general  formula  for  the  alcohols  we  make 
•n  =  o,  the  formula  becomes  H202  =  2HO,  which  represents  2  atoms 
j)f  water.  Water  is  therefore  said  to  be  the  type  of  the  series.  In  like 

QUESTIONS. — May  there  be  other  homologizing  bodies  ?  547.  What  is 
said  of  the  effect  of  reagents  upon  homologous  bodies  of  the  same  series? 
Into  what  are  the  alcohols  converted  by  oxydizing  reagents  ?  What  inter- 
mediate product  is  obtained  in  some  cases  ?  What  are  contained  in  the 
table  in  this  paragraph  ?  548.  What  is  said  of  the  oxygen  and  nitrogen 
in  the  homologous  series  now  known  ?  Why  is  water  said  to  be  the  type 
of  the  series  of  alcohols  ? 


404  GENERAL   PROPERTIES   OF   ORGANIC   BODIES. 

manner  the  general  formula  for  the  oleic  acids,  C2«H2(W — j)04,  when 
»  =  1,  becomes  C204  =  2C02;  the  type  of  the  series  is  therefore  car- 
bonic acid,  C02. 

549.  Although  all  the  compounds  of  any  homologous  series  are  essen- 
tially similar  in  their  leading  properties,  yet  we  may  often  observe  a 
gradual  transition  as  we  pass  from  one  to  another  of  the  same  series. 
The   carbo-liydrogens    (Hydrogens   and   Acetencs,    p.  402  ,)    having   the 
smallest  number  of  atoms  are  gaseous  at  ordinary  temperatures,  but 
as  we  ascend  in  the  series,  that  is,  as  the  number  of  atoms  in  the  com- 
pound is  increased,  they  become  less  and  less  volatile,  until  the  higher 
members  of  the  series,  at  the  ordinary  temperature,  are  liquid,  or  even 
solid.     Methylic  alcohol,  the  first  in  the  alcohol  series,  boils  at  152°,  and 
the  others  have  each  a  higher  boiling  point  in  proportion  as  the  number 
of  atoms  is  increased.     The  last  three  are  solid  at  ordinary  temperatures. 
In  general,  in  any  series,  the  boiling  point  becomes  higher  as  the  whole 
number  of  atoms  in  the  compound  is  greater. 

550.  Analysis  of  Organic  Substances. — The  analysis  of  a  compound  has 
for  its  object  to  determine  its  composition ;  and  in  organic  chemistry  may 
be  either  proximate  or  ultimate.     By  the  proximate  analysis  of  a  substance 
we  separate  and  determine  its  proximate  principles,  or,  in  other  words, 
the  several  organic  compounds  which  may  be  contained  in  it,  as  sugar, 
gum,  albumen,  &c. ;  but  by  its  ultimate  analysis  we  determine  its  ultimate 
elements,  as  carbon,  hydrogen,  nitrogen,  &c.     The  methods  of  separating 
the  proximate  principles  will  be  described  as  we  progress,  but  for  general 
modes  of  analyses  the  intelligent  student  will  consult  works  treating 
specially  of  Analytical  Chemistry.. 

551.  Proximate  principles  are  the  proper  organic  compounds,  which 
cannot  be  separated  into  other  kinds  without  evidently  changing  their 
nature ;   they  are  usually  characterized  by  one  or  more  of  the  following 
properties,  viz. : 

1.  Capability  of  combining  in  definite  proportions  with  other  elementary 
substances,  or  well  determined  compounds. 

2.  Capability  of  crystalizing,  when  obtained  in  the  solid  state,  or  having 
a  definite  melting  point. 

3.  Having  a  definite  boiling  point,  and  being  capable  of  distillation,  or 
sublimation,  without  decomposition,  or  a  change  of  properties. 

The§e  compounds  are  seldom  found  uncombined  in  organized  bodies, 
and  their  separation,  or  the  proximate  analysis  of  the  substances  con- 
taining them,  becomes  an  important  object  to  the  chemist,  and  is  often 
attended  with  no  little  difficulty. 

QUESTIONS. — 549.  Do  we  observe  a  gradual  transition  in  the  properties 
of  the  members  of  a  homologous  series  as  we  pass  from  one  to  another  ? 
Give  an  instance  to  illustrate.  550.  Define  what  is  meant  by  the  proxi- 
mate and  what  by  the  ultimate  analyses  of  an  organic  compound.  What 
is  a  proximate  principle?  551.  What  are  the  characteristics  by  one  or 
more  of  which  an  organic  compound  will  usually  be  distinguished  ? 


STARCH. 


405 


STARCH,    SUGAR,    GUM,   LIGNINE. 

552.  These  four  organic  bodies  constitute  a  natural  family, 
possessing  this  remarkable  peculiarity,  that  each  member  is 
composed  of  'twelve  atoms  of  carbon,  united  with  a  certain  num- 
ber of  atoms  of  water,  or  rather  with  the  elements  of  water, 
oxygen  and  hydrogen.  In  general,  they  are  nutritious  sub- 
stances, and  do  not  possess  any  very  active  chemical  affinities. 


STARCH,     OR    TECULA,     C12H10010. 

553.  Sources. — Starch,  or  fecula,  is  obtained  from  a  variety 
of  vegetable  substances,  as  the  different  grains ;  and  from  many 
roots,  as  the  potato ;  and  also  sometimes  from  the  stems  of  plants. 
It  is  contained  in  the  cavities  of  the  vegetable  tissues,  in  the  form 
of  small,  white  grains,  which  always  have  a  rounded  outline,  but 
vary  considerably  in  size  and  form,  as  obtained  from  different  sub- 
stances. Each  grain  is  inclosed  in  a  delicate  envelope  that  is  not 
readily  acted  upon  by  cold  water,  but  is 
ruptured  by  the  expansion  of  the  inclosed 
substance,  when  the  water  is  heated  nearly 
to  the  boiling  point. 

To  show  the  appearance  of  the  starch 
globules,  in  their  cells  in  the  vegetable 
tissue,  cut  a  very  thin  slice  of  a  potato, 
and  examine  it  carefully  by  means  of  the  Section  of  potato, 

compound  microscope; — their  appearance  will  be  much  as  repre- 
sented in  the  above  figure. 

If  the  slice  before  examination  is 
moistened  with  a  very  dilute  alcoholic 
solution  of  iodine,  the  starch  globules 
will  be  colored  blue,  while  the  other 
parts  remain  uncolored. 

The  next  figure  shows  the  arrange- 
ment of  the  starch  globules  in  a  grain  starch  Globules  in  a  Grain  of  ny«. 

QUESTIONS.  —  552..  Of  what  are  starch,  sugar,  gam,  &c.,  composed? 
553.  From  what  is  starch  obtained  ?  How  is  each  grain  inclosed  ?  How 
may  the  grains  of  starch  be  shown  in  the  potato  ? 


406 


STARCH. 


of  rye.  A,  the  outer  seed-coat,  which  constitutes  the  bran  after 
grinding;  B,  the  gluten  (to  be  described  hereafter);  and  C,  the 
grains  of  starch. 

The  grains  of  starch  from  .different  sources  vary  greatly  in  size, 
and  present  different  outlines.  Of  the  following  figures,  A  repre- 
sents starch  grains  of  the  potato,  B  those  of  wheat,  and  G  those 
of  peas. 

ABC 


Starch  Grams  of  the  Potato. 


Ditto  of  Wheat. 


554.  Preparation  and  Properties. — Starch  is  easily  obtained 
from  potatoes  by  mashing  the  tubers,  and  then  inclosing  the  pulp 

in  a  piece  of  cloth,  and 
washing  it  freely  with 
cold  water,  at  the  same 
time  pressing  the  mass 
between  the  hands. 

From  wheat  or  rye 
flour  it  is  easily  procured 
by  placing  the  flour  upon 
a  piece  of  muslin,  and 
working  it  with  the  hand 
while  a  small  stream  of 
water  is  poured  upon  it. 
The  starch  is  washed 
through  with  the  water, 
while  the  gluten  remains 
as  a  tenacious  mass  upon  the  muslin.  After  a  few  hours  the  starch 
will  all  subside. 


Separating  Starch  from  Wheat  Flour. 


QUESTIONS. — What  is  said  of  the  appearance  of  starch  globules  from 
different  sources  ?  554.  How  may  starch  bo  obtained  from  the  potato  t 
How  from  wheat  or  rye  flour  ? 


STARCH.  407 

Starch  is  an  insipid  white  solid,  quite  insoluble  in  cold,  but 
slightly  soluble  in  boiling  water.  In  the  latter  case,  the  granules 
are  broken,  and  the  broken  envelopes  floating  in  the  solution  give 
it  the  consistence  of  a  jelly.  In  this  state  it  is  used  for  stiffening 
linen. 

Though  quite  insipid  to  the  taste,  it  forms  a  large  part  of  many 
articles  of  food,  as  the  different  grains,  rice,  the  potato,  and  qjther 
esculent  roots.  It  also  performs  important  functions  in  nearly 
all  vegetables  during  their  growth. 

The  substances  known  as  arrow-root,  tapioca,  and  sago  are 
different  varieties  of  starch. 

Iodine  forms  with  starch  a  beautiful  blue  compound,  which  is  quite 
insoluble  in  water ;  it  therefore  serves  as  an  excellent  test  for  it. 

555.  When  starch  is  kept  for  some  time  at  a  temperature  between  300° 
and  400°,  it  undergoes  a  peculiar  cha»ge,  and  becomes  soluble  in  cold 
water,  and  is  called  British  gum,  or  leiocome. 

A  substance  very  similar  to  the  above,  but  called  dextrine,  is  produced 
by  gently  heating  starch  in  water  acidulated  with  sulphuric  acid,  or  con- 
taining infusion  of  malt.  It  has  the  same  composition  as  starch,  but  is 
very  soluble  in  cold  water,  and  is  not  colored  by  iodine.  If  the  mixture 
is  boiled  for  some  time,  grape-sugar  is  formed,  of  which  more  will  be  said 
hereafter. 

Diastase  is  a  substance  produced  in  small  quantity  in  the  process  of 
malting  grain,  and  is  found  in  the  potato  soon  after  germination  coni- 
menc*es,  in  the  parts  near  the  young  germs.  It  is  noted  for  its  specific 
action  upon  starch,  converting  it  first  into  dextrine,  in  the  same  manner 
as  diluted  sulphuric  acid,  and  afterwards  into  grape-sugar.  Diastase 
is  known  to  contain  nitrogen,  but  its  composition,  further  than  this, 
has  not  been  well  determined. 

556.  The  operation  of  malting  consists  in  exposing  grain  (usually  bar- 
ley) to  the  proper  degree  of  heat  and  moisture,  with  the  free  accession 
of  atmospheric  air,  to  produce  incipient  germination,  and  then  suddenly 
checking  it  by  elevating  the  temperature.     This  is  done  by  first  soaking 
the  grain  in  water  until  it  is  fully  swelled,  and  then  placing  it  in  heaps 
upon  a  floor  until  it  begins  to  germinate,  when  the  further  progress  of  the 
vegetable  process  is  arrested  by  quickly  drying  it  at  a  moderately-elevated 
temperature.     During  the  incipient  germination,  a  portion  of  diastase  is 
produced,  by  which,  in  the  subsequent  processes  to  which  the  grain  is 
subjected,  much  of  the  starch  of  the  grain  is  converted  into  dextrine  and 
grape-sugar ;.  and  the  grain  (now  called  malt)  becomes  fitted  for  the  us"e 
to  which  it  is  applied.     It  is  chiefly  used  in  the  manufacture  of  beer. 

QUESTIONS.— What  is  said  of  the  properties  of  starch  ?  What  varieties 
of  it  are  mentioned  ?  555.  What  test  of  starch  is  mentioned  ?  How  is 
starch  affected  by  a  heat  of  300°  or  400°  ?  What  is  dextrine  ?  What 
diastase  9  656.  What  is  malt  ?  What  use  is  made  of  malt? 


408  SUGARS. 


SUGARS. 

557,  There  are  several  varieties  of  sugar,  but  the  most  important 
are  cane  and  grape-sugar, — names  suggested  by  the  sources  from 
which  they  are  respectively  obtained.     All  the  varieties  of  sugar 
possess  a  sweet  taste,  are  soluble  in  water,  and  are  susceptible 
of  undergoing  a  peculiar  change,  called  the  vinous  fermentation, 
by  which  alcohol  is  produced. 

558.  Cane-Sugar,  C12HnOn. — Most  of  the  sugar  of  commerce 
is  obtained  from   the   sugar-cane  (arundo  saccharifcra),   repre- 
sented in  the  figure ; — scale,  one  inch  to 
four  feet.     But  it  is  procured  also  in  this 
country  in  large  quantities  from  the  sap 
of  the  sugar-maple  (acer  saccharinuiri). 
Many  plants  contain  it  in  their  juices,  as 
the  common  beet  and  other  roots,  and 
the  stalks  of  Indian  corn.     Their  juices, 
after  being  expressed  from  the  plant,  are 
evaporated  until  a  dense  syrup  is  obtained, 
from  which  a  large  portion  of  the  sugar 
crystalizes  on  cooling;  and  the  remaining 
liquid  portion  is  then  drained  oflf,  and 
constitutes  treacle,  or  molasses. 

Pure  sugar  is  a  white,  inodorous  sub- 
stance, of  a  very  agreeable,  sweet  taste, 
which  it  imparts  to  its  solutions.  By 
slow  evaporation,  in  a  very  warm  room, 
it  is  obtained  in  large  rhomboidal  crys- 
tals, which  are  sold  as  rock-candy.  It 
is  very  soluble  in  water,  but  is  dissolved 
Sugar-cane.  on]y  jn  gmau  quantity  in  alcohol.  Its 

density  is  1-6.     It  melts  at  about  356°,  and  on  cooling  forms  a 
transparent,  vitreous  mass,  called  Parley-sugar ',  which,  however, 

QUESTIONS. — 557.  How  are  the  sugars  characterized  ?  558.  From  what 
is  cane-sugar  obtained  ?  Give  some  of  the  properties  of  sugar  ?  Wha* 
is  barley-sugar  ? 


SUGARS.  409 

after  a  time,  becomes  white  and  opaque,  and  is  then  found  to  be 
a  mass  of  small  crystals.     Its  composition  remains  without  change. 

By  heating  cane-sugar  to  420°  or  425°,  a  change  of  composition  is 
effected ;  it  then  gives  up  2  atoms  of  water,  and  a  brown  substance  is 
formed,  called  caramel,  which  has  the  composition,  Ci2Hg09. 

559.  Grape-sugar-Glucose,  CBHM0M=  C12H12012  +  2H(X— 
This  substance,  which  much  resembles  the  preceding,  has  -for  its 
composition,  when  crystulized,  C,2H,4Q14;  but  by  a  boiling  heat, 
two  equivalents  of  water  are   expelled.      It  is  more  generally 
diffused  in  nature  than  cane-sugar,  being  found  in  the  grape  and 
most  other  sweet  fruits.    It  constitutes  also  the  solid  part  of  honey. 
It  may  be  obtained  from  grapes  by  expressing  the  juice,  and  neu- 
tralizing the  free  acid  with  chalk,  and  then  clarifying  and  crys- 
talizing  in  the  same  manner  as  with  cane-sugar. 

Grape-sugar  is  less  soluble  in  water,  and  forms  a  less  tenacious 
syrup,  and  is  less  sweet  than  cane-sugar.  One  ounce  of  water 
will  dissolve  three  ounces  of  cane-sugar,  but  only  about  two-thirds 
of  an  ounce  of  grape-sugar ;  and  it  is  estimated  that  one  ounce 
of  the  former  has  an  equal  sweetening  capacity  with  two  and  a 
half  ounces  of  the  latter.  Grape-sugar  does  not  crystalize  as 
readily  as  cane-sugar,  and  is  soluble  in  oil  of  vitriol,  while  cane- 
sugar  is  blackened  by  it. 

A  dilute  solution  of  sulphate  of  copper,  containing  a  little  potassa,  or 
tartrate  of  potassa,  is  at  once  rendered  colorless  by  grape-sugar,  at  the 
ordinary  temperature,  but  this  effect  is  produced  by  cane-sugar  only  by 
boiling.  This  serves  as  an  unfailing  test  to  distinguish  the  two  varieties 
of  sugar.  The  color  of  the  copper  solution  is  destroyed  by  the  precipita- 
tion of  suboxide  of  copper,  Cn20. 

560,  Grape-sugar  may  be  prepared  from  several  substances 
which  have  a  similar  composition,  as  starch,  gum,  and  woody- 
fibre  or  lignine,  and  is  occasionally  found  in  the  animal  system, 
as  in  the  disease  called  diabetes.     It  then  makes  its  appearance 
in  the  urine.     It  is  sometimes  called  starch,  sugar,  diabetic  sugar, 
and  glucose.     The  latter  name  is  more  properly  applied  to  the 

QUESTIONS. — What  is  caramel?  559.  Describe  grape-sugar.  What  is 
said  of  its  solubility  in  water  and  its  sweetness,  as  compared  with  cane- 
Bugar?  How  may  the  two  kinds  be  distinguished  from  each  other? 
660.  Describe  the  mode  of  preparing  grape-sugar,  or  glucose,  from 
itarch. 

35 


410  SUGARS. 

sugar  prepared  from  starch,  &c.3  but  the  identity  of  this  substanoo 
with  the  sugar  of  grapes  is  generally  admitted. 

To  prepare  grape-sugar  from  starch,  1  part  of  sulphuric  acid  is  mixed 
•with,  200  parts  of  water,  and  heat  applied  'until  the  mixture  begins  to 
boil  ;  50  parts  of  starch  are  then  added,  and  the  boiling  continued  until 
the  liquid  becomes  perfectly  clear.  Powdered  chalk  is  then  introduced, 
a  li  ttle  at  a  time,  in  order  to  neutralize  the  acid  ;  and  by  a  few  hours 
standing  the  sulphate  of  lime  formed  will  be  precipitated,  leaving  the 
liquid  clear,  which  is  now  solution  of  glucose.  By  evaporation  of  the 
,  water  it  may  be  obtained  in  crystals. 

Wood,  the  composition  of  which,  as  we  shall  hereafter  see,  is  nearly 
the  same  as  that  of  starch,  also  yields  grape-sugar,  or  glucose,  by  boiling 
with  sulphuric  acid.  The  process  is  essentially  the  same  as  the  above, 
except  that  a  large  proportional  quantity  of  the  acid  is  used. 

In  both  of  these  processes  the  acid  remains  unchanged,  but  by  its  pre- 
sence, in  some  unexplained  mode,  it.  occasions  the  starch  and  the  cellulose 
of  the  wood  to  unite  with  an  additional  quantity  of  water  —  or  the  elements 
of  water  —  thus  converting  it  into  sugar.  Thus, 

Starch  (or  cellulose),  C12H100,0  +  4HO  =  C12H14014. 

From  clean  linen,  or  cotton  rags,  more  than  their  own  weight  of  sugar 
may  be  formed. 

Grape-sugar,  prepared  in  this  way,  is  used  £o  adulterate  cane-sugar, 
and  in  the  manufacture  of  beer  and  alcohol. 

Sugar  of  sour  fruits,  as  currants,  cherries,  plums,  &c.,  possesses  the 
composition,  C,2H120,2,  and  readily  ferments,  producing  alcohol,  but  is 
uncrystalizable. 


561.  Milk  Sugar,  Lactine,  CaJI^O^  =  C^H^O^  -f  5HO.—  This  sweet 
principle  is  obtained  by  evaporating  the  whey  of  milk,  purifying  with 
animal  charcoal,  and  crystalizing.     It  is  less  soluble  in  water  than  either 
of  the  other  varieties  of  sugar,  and  less  sweet  to  the  taste.     Under  cer- 
tain circumstances,  it  is  capable  of  undergoing  the  alcoholic  fermentation, 
like  the  other  varieties  of  sugar  ;  and  in  some  countries,  it  is  well  known 
that  an  intoxicating  drink  is  made  from  camels'  milk.     But  when  in 
solution  it  is  allowed  to  stand  in  the  open  air,  at  ordinary  temperatures, 
lactic  fermentation  takes  place,  and  lactic  acid,  C6H606  =  C6H505,HO,  is 
formed.     This  change  takes  place  in  the  ordinary  souring  of  milk.     By 
the  action  of  dilute  acids  at  212°,  lactine  is  converted  into  grape-sugar. 

562.  ilannite,  C6H706,  though  not  analogous  to  sugar  in  composition, 
is  similar  to  it  in  some  of  its  properties.     It  is  found  in  many  plants, 

it  chiefly  in  a  substance,  called  manna,  obtained  from  certain  speciea 
jf  the  ash. 

QUESTIONS.  —  Describe  the  mode  of  preparing  grape-sugar  from  wood. 
Does  the  acid  remain  unchanged  in  the  operation  ?  What  is  said  of  the 
sugar  of  sour  fruits?  561.  What  is  milk-sugar,  or  lactine?  May  it 
undergo  the  alcoholic  fermentation  ?  5*62.  Describe  mannite. 


GUMS. — WOODY    FIBAE. 


GUMS,     CI2H10O10. 

563.  We  designate  by  the  name  of  gum  a  variety  of  vegetable 
substances,  which  are  very  soluble  in   water,  but  insoluble   in 
alcohol,  and  uncrystalizable.     Their  composition  is  the  same  as 
that  of  starch,  but  they  differ  from  this  substance  in  several 
of  their  properties. 

The  gums  generally  exude  from  the  bark  of  trees,  as  the 
cherry  and  peach  trees,  and  are  found  on  the  outside  in  trans- 
parent masses,  which  are  more  or  less  globular  in  form. 

A  gum  is  a  colorless,  transparent,  insipid,  inodorous  solid,  and 
when  perfectly  dry  is  very  brittle,  and  has  a  vitreous  fracture. 
When  put  into  water,  it  first  so'ftens  and  swells  up  considerably, 
and  then  dissolves,  forming  a  mucilage  which  is  often  used  as  a 
substitute  for  paste,  for  which  it  answers  well.  Its  solubility  is 
increased  both  by  acids  and  alkalies.  Gum  Arabic,  gum  Sene- 
gal, and  gum  tragacanth  are  the  most  common  varieties  of  this 
substance. 

Solutions  of  gum  Arabic,  and  probably  also  those  of  the  other  gums, 
yield  sugar  by  boiling  with  sulphuric  acid; — boiled  with  nitric  acid, 
mucic  acid  is  formed. 

564.  Pectine  is  a  substance  closely  resembling  gum,  which  is  found  in 
many  fruits  and  in  certain  roots  ;  it  is  the  substance  contained  in  cur- 
rants, cherries,  apples,  &c.,  which  they  yield  on  being  boiled,  and  espe- 
cially when  boiled  with  sugar.     It  is  a  kind  of  vegetable  mucus,  and 
found  in  small  quantity  in  many  vegetables.     By  the  action  of  an  alkali, 
or  almost  any  base,  it  is  converted  into  an  acid,  called  pectic  acid. 


WOODY    FIBRE,     LIGNINE,     CELLULOSE. 

565.  Wood  from  a  growing  tree  is  of  a  very,  complex  compo- 
sition. By  examination  with  the  microscope,  it  is  found  to 
possess  a  highly  organized  structure  (533),  consisting  of  vascular 
tissue,  having  its  cells  filled  with  a  variety  of  substances,  as 
starch,  solution  of  sugar  and  mineral  salts,  albuminous  com- 

QUESTIONS. — 563.  Describe  the  gums.  From  what  are -they  obtained? 
What  are  some  of  the  varieties  of  gum?  How  are  the  gums  affected  by 
sulphuric  acid  ?  By  nitric  acid  ?  564.  Describe  pectine.  565.  What  is 
said  of  the  composition  of  growing  trees  ?  ' 


412 


W  O  O-D  Y     FIBRE. 


Section  of  Stem. 


pounds,  oils,  and  resins,  depending  upon  the  natural  family  and 
species  to  which  the  tree  belongs. 

The  first  figure  in  the  margin  repre- 
sents a  transverse  section  of  the  stem 
of  a  tree.  A  is  the  outer  bark,  which 
is  usually  rough,  and  has  lost  its  vitality, 
and  serves  only  as  a  covering  to  the 
parts  'within.  B  is  the  inner  fibrous 
bark,  in  which  the  sap-vessels  are 
found,  serving  the  purpose  of  the 
veins  of  animals.  Inside  of  this  is 
the  wood,  consisting  of  the  part  C, 
which  is  usually  whiter  than  the  rest,  and  is  therefore  called  the 
alburnum,  or  sap-wood;  and  the  heart-wood,  D,  which  is  more 
solid  and  durable  than  the  sap-wood,  and  of  a  darker  color.  Both 
the  alburnum  and  the  heart-wood  are  composed  of  concentric 
layers,  an  addition  of  a  layer  being 
made  to  the  alburnum  each  year,  im- 
mediately beneath  the  bark.  The  next 
figure  represents  a  transverse  section, 
B  magnified,  of  a  piece  of  pine,  showing 
the  two  kinds  of  wood — A,  the  albur- 
num; B,  the  heart-wood.  The  inner 
rings  of  the  alburnum  are  gradually 
converted  into  firm  heart-wood,  and  seem  then  no  longer  to 
partake  of  the  vitality  of  the  tree.  In  annual  plants,  the  woody 
part  corresponds  to  the  alburnum  of  trees. 

566.  Cellulose,  C12H100,0. — The  vascular  tissue  of  which  we  have 
spoken  is  composed  chiefly  of  cellulose,  the  composition  of  which,  it 
will  be  observed,  is  the  same  as  that  of  starch,  though  it  differs  essen- 
tially from  this  substance  in  some  of  its  properties. 

Cellulose  constitutes  the  basis  of  wood,  and  is  obtained  by  digesting 
saw-dust,  paper,  or  linen  or  cotton  rags,  successively  in  alcohol,  ether, 
diluted  acid,  diluted  alkaline  solutions,  and  water,  so  as  to  remove  every- 
thing which  is  soluble  in  these  menstrua. 

It  is  found  in  very  different  states ;  as  indigestible  and  hard,  in  wood, 
and  in  the  shells  of  nuts ;  as  tender  and  easily  digestible,  in  the  esculent 

QUESTIONS.  — What  is  represented  by  the  first  figure  on  this  page  ? 
What  by  the  second?  566.  In  what  is  cellulose  found?  What  is  said 
of  its  composition  ? 


Section  of  Pine. 


WOODY     FIBRE.  413 

roots,  and  in  the  pulp  of  fruits,  as  the  apple,  pear,  &c. ;  as  light  and 
porous,  in  the  pith  of  the  elder,  and  in  cork ;  and  as  soft  and  flexible,  in 
the  fibres  of  cotton,  flax  and  hemp. 

587,  Lignine,  Woody  Fibre. — The  vascular  tissue  of  plants, 
when  first  formed,  is  composed  of  nearly  pure  cellulose.,  but  after- 
wards the  cells  become  lined  with  a  hard  incrusting  substance, 
which,  in  trees  and  shrubs,  for  years  increases  in  thickness  and, 
solidity.  This  is  called  lignine,  or  sometimes  woody  fibre,  though 
the  latter  term  is  more  properly  applied  to  wood  as  found  in  the 
tree,  and  composed  of  both  cellulose  and  lignine.  Lignine  is 
found  more  abundant  in  the  heart-wood  than  in  the  alburnum. 

The  composition  of  lignine  is  believed  to  be  essentially  the  same  as 
that  of  cellulose,  but  it  has  not  been  fully  determined. 

We  have  seen  above  (560),  that  wood  treated  by  sulphuric  acid  is  con- 
verted into  grape-sugar,  but  it  is  only  the  cellulose  that  is  capable  of  this 
change ;  lignine  is  not  affected  by  sulphuric  acid,  or  only  charred. 

The  mutual  relations  of  starch,  sugar,  and  woody  fibre,  are  singular 
and  important.  Their  composition,  we  have  seen,  is  nearly  the  same ; 
and  they  are  convertible  into  each  other  by  easy  processes ;  indeed,  we 
are  able  to  recognise  this  conversion  as  really  taking  place,  in  certain 
cases,  in  the  natural  process  of  vegetation,  as  shown  in  the  malting 
of  grain.  The  same  change  takes  place  in  the  ripening  of  many  fruits, 
as  the  apple  and  pear,  which  are  acid  until  they  approach  maturity,  when 
they  become  more  or  less  sweet.  The  sap  of  the  maple  and  other  trees 
contain  sugar,  which  subsequently  becomes  changed  into  woody  fibre, 
and  thus  contributes  to  the  enlargement  of  the  tree. 


Changes  produced  upon  Woody  Fibre  by  Acids. 

568,  Wood,  plunged  into  strong  sulphuric  acid,  especially  if 
a  little  warm,  is  instantly  charred,  as  if  held  near  a  hot  fire. 
This  is  occasioned,  it  is  believed,  by  the  strong  affinity  of  the 
acid  for  water,  the  elements  of  which,  oxygen  and  hydrogen,  are 
abstracted  by  it  from  the  wood,  leaving  the  black  carbon. 

If  the  sulphuric  acid  be  diluted,  or  if  added  in  small  quantities, 
so  as  entirely  to  avoid  any  rise  of  temperature,  the  effect  is  to  form 
sugar,  as  we  have  already  seen. 

QUESTIONS. — 567.  In  what  is  lignine  or  woody  fibre  found  ?     What  is 
said  of  the  mutual  relations  of  starch,  sugar,   and  woody  fibre?     Are 
they  capable  of  conversion  one  into  another?     568.  What  is  the  effect 
ot  strong  sulphuric  acid  upon  wood  ?     What  if  the  acid  is  diluted  ? 
35* 


414  WOODY    FIBRE. 

569.  Gun  Cotton  —  Pyroxyline. — This  substance,  which  is 
noted  for  its  explosive  property,  is  formed  by  the  action  of  very 
strong  nitric  acid,  or  better,  by  a  mixture  of  the  most  concen- 
trated nitric  and  sulphuric  acids,  upon  cotton,  flax,  paper,  or 
fine  saw-dust. 

To  prepare  it,  make  a  mixture  of  equal  parts  (by  volume)  of  the 
strongest  nitric  and  sulphuric  acids,  and  then  press  into  it  as  nvjch 
cotton  as  can  be  moistened  with  it;  and,  after  standing  five  or  ten 
minutes,  press  out  as  much  of  the  acid  as  possible,  and  wash  thoroughly 
with  a  large  supply  of  pure  water,  and  dry  carefully  without  artificial 
heat.  It  will  be  found  that  two  ounces  of  each  of  the  mixed  acids  will  be 
sufficient  for  75  or  100  grains  of  cotton. 

When  thus  prepared,  the  cotton  appears  much  as  before  the  process, 
but  has  a  harsh  feeling,  and  the  fibres  are  less  tenacious  than  in  the 
original  cotton.  It  also  gains  considerably  in  weight  during  the  process, 
so  that  from  100  grains  of  cotton  as  much  as  175  grains  of  gun-cotton 
will  often  be  obtained.  It  takes  fire  very  readily,  often  at  a  temperature 
even  below  212°,  especially  if  the  heat  is  suddenly  applied ;  and  burns 
with  an  immense  volume  of  flame.  Placed  on  a  plate  of  metal,  and  very 
gradually  heated,  it  may  sometimes  be  completely  decomposed,  without 
igniting,  leaving  behind  a  residue  of  carbon.  When  properly  prepared, 
it  explodes  with  great  violence,  and  is  entirely  consumed.  Its  power  to 
propel  balls  is  much  greater  than  that  of  the  best  gunpowder,  which  is  still 
further  increased  by  soaking  it  in  a  solution  of  chlorate  of  potash  before 
drying. 

The  composition  of  pyroxyline  is  is  uncertain;  but  it  is  known  that, 
by  the  action  of  the  acids,  oxygen  and  hydrogen  (in  the  form  of  water) 
are  separated  from  the  cotton,  and,  at  the  same  time,  nitric  acid  com- 
bines with  it.  The  most  probable  opinion  is  that  2  equivalents  of  cellulose 
combine  with  5  equivalents  of  nitric  acid,  giving  up  at  the  time  3  equiva- 
lents of  water.  Thus, 

C2<tt*00y>+  5N05  =  C24H17017,6N06  4.  3HO. 

Gun-cotton,  though  insoluble  in  water  or  alcohol,  is  usually  found  quite 
soluble  in  sulphuric  ether  containing  a  little  alcohol.  But  this  is  not 
always  the  case ;  and  it  is  believed  there  are  at  least  two  different  com- 
pounds formed  in  the  process,  one  of  them  being  soluble  in  alcoholic  ether, 
and  the  other  insoluble.  The  insoluble  variety  appears  also  to  explode 
with  more  violence  than  the  other. 

The  gelatinous  ethereal  solution  of  gun-cotton  is  used  in  surgery,  as  a 
substitute  for  sticking-plaster,  or  court-plaster,  under  the  names  of  col- 
lodion and  liquid  cuticle. 

JTyloidine  is  an  explosive  compound  similar  to  pyroxyline,  produced  by 
the  action  of  strong  nitric  acid  upon  starch. 

QUESTIONS. — 569.  Describe  the  process  of  preparing  gun-cotton.  Give 
its  properties.  What  is  the  most  probable  opinion  concerning  the  com- 
position of  pyroxyline,  or  gun-cotton  ?  In  what  is  it  soluble  ?  What  is 
xyloidine  ? 


WOODY    FIBRE  415 


Changes  of  Woody  Fibre,  by  Air  and  Moisture. 

570.  When  lignine  is  kept  perfectly  dry,  or  constantly  im- 
mersed in  water,  it  may  be  preserved  for  any  length  of  time; 
but  exposed  to  air  and  moisture,  it  undergoes  a  slow  decay,  called 
eremacausis  (from  erema,  slow,  and  kausis,  combustion),  by  tho 
absorption  of  oxygen,  and  the  evolution  of  water,  or  its  elements, 
and  carbonic  acid. 

The  chemical  changes  which  in  this  case  occur,  are  very  nearly 
the  sLrae  as  in  combustion,  except  that  they  take  place  more  slowly. 
In  both  cases,  the  constituents  of  the  wood,  with  the  addition  of 
oxygen  from  the  air,  are  converted  into  carbonic  acid  and  water; 
in  both  cases,  also,  the  hydrogen  is  oxydized  more  rapidly  than 
the  carbon,  as  is  shown  by  the  black  color  during  combustion, 
and  the  dark  brown  during  the  slow  decay  of  vegetable  matter. 
The  flame  which  appears  during  the  combustion  of  wood  and 
other  vegetable  substances,  is  occasioned  by  the  burning  of  the 
gaseous  hydro-carbons,  evolved  as  the  first  effects  of  the  application 
of  heat. 

571.  Humus,  Geine. — Every  fertile  soil  contains  more  or  less  organic 
matter  in  a  state  of  decay,  to  which  its  fertility  is,  in  a  great  measure, 
owing,  and  which  has  received  various  names,  as  humus,  geine,  ulmine, 
vegetable  mould,  humic,  geic,  and  ulmic  acids,  &c.     This  decaying  matter, 
which  we  will  call  vegetable  mould,  is  ever  changing,  as  the  carbon  and 
hydrogen  are  oxydized  and  separated ;   and  from  this  and  the  carbonic 
acid,  water,  and  ammonia,  formed  from  them  in  the  soil,  the  plants  derive 
their  chief  nourishment,  by  means  of  their  roots,  which  are  extended  in 
every  direction. 

572.  Peat. — Peat  consists  of  partially  decayed  vegetable  matter,  which 
is  found  in  beds,  in  moist  places,  in  every  country,  and  is  usually  mixed 
with  more  or  less  matter  of  mineral  origin.     It  is  formed  from  vegetable 
matter  when  slowly  decaying  under  water,  and  of  course  free  from  the 
influence  of  the  oxygen  of  the  air.     Water  is  decomposed,  yielding  its 
oxygen  to  one  portion  of  carbon,  to  produce  carbonic  acid,  while  another 
portion  of  carbon  unites  with  the  hydrogen,  forming  light  carburetted 
hydrogen  (307),  which  often  issues  from  the  soil  in  large  quantities,  as 
the  fire-damp  of  coal  mines ;   but  most  of  the  carbon  remains  behind  as 
peat.    Recently  formed  peat  is  also  usually  found  interlaced  witli  tha 

QUESTIONS. — 570.  May  wood^  be  preserved  if  kept  perfectly  dry? 
What  is  the  eifect  when  exposed  to  air  and  moisture?  What  is  said 
of  the  chemical  changes  which  take  place  in  eremacausis?  571.  What 
is  contained  in  every  fertile  soil  ?  572.  Describe  the  formation  of  peat. 


116  WOODY    FI-BRE. 

fibrous  roots  of  growing  plants,  and  retains,  more  or  less  distinctly,  the 
forms  of  many  of  the  plants  of  which  it  has  been  composed ;  but  old  peat 
is  more  homogeneous,  and  may  be  cut  into  the  form  of  bricks,  like  moist 
clay.  In  many  countries  it  is  used  extensively  for  fuel,  being  first 
thoroughly  dried. 

573.  Coal. — A  sufficient  description  of  the  different  kinds  of  mineral 
coal  has  already  (298)  been  given.     Immense  deposits  of  this  mineral 
nre  found  in  many  countries,  which  have  no  doubt  been  formed  from 
vegetable  matter,  at  a  comparatively  early  period  in  the  world's  history. 
They  are  usually  not  very  distant  beneath  the  surface ;   and  are  con- 
tained between  rocky  strata  of  great  extent.   .  Occasionally  these  strata 
are  covered  with  many  feet  of  rock  and  earth ; — everything  indicating 
that  vast  changes  ha've  taken  place  in  the  earth's  surface  since  their 
formation. 

That  all  the  varieties  of  mineral  coal  have  been  produced  from  the 
matter  of  plants,  which  in  former  periods  grew  up  and  flourished  pre- 
cisely as  plants  now  do,  is  universally  believed  by  men  of  science.  The 
evidence  is  found  in  the  position  of  the  coal,  which  always  occurs  in  the 
form  of  beds  interstratified  above  and  below  .with  solid  rock  formed  at 
the  same  time  with  itself ; — -in  the  vegetable  impressions  which  abound 
in  the  rocky  strata  of  every  coal  formation; — and  in  the  organized 
structure  often  exhibited  by  the  coal  itself. 

We  may  suppose  that,  by  the  decay  of  the  vegetable  matter,  peat  was 
first  produced,  which  was  subsequently  converted  into  proper  .coal,  in  a 
manner  not  fully  understood. 

Mines  of  coal  are  limited  to  the  temperate  zone,  none  of  it  being  found 
in  very  warm  or  very  cold  climates. 

574.  Petroleum.— Petroleum,  or  rock-oil,  is  an  odoriferous,  oily  liquid, 
which,   in  many  countries,   exudes  from  the  rocks  and  ground,  being 
formed,  in  all  probability,  from  vegetable  matter  at  the  same  time  with 
peat  and  coal.     It  is  often  found  upon  the  surface  of  lakes  and  springs, 
as  at  Seneca  Lake  in  New  York,  where  it  is  called  Seneca  oil.     By  distil- 
lation, petroleum  yields  a  yellowish  liquid,  lighter  than  water,  called 
naphtha,  or  oil  of  naphtha ;  which  is  probably  a  mixture  of  several  com- 
pounds that  have  not  yet  been  separated.     It  is  the  liquid  used  to  pre- 
serve the  alkaline  metals.     Asphaltum,  or  mineral  pitch,  is  a  substance 
closely  allied  to  petroleum.     When  cold  it  is  solid,  but  becomes  soft  as  it 
is  heated,  and  melts  at  about  212°.     Dissolved  in  oil  of  turpentine,  it 
forms  a  varnish  which  is  used  for  certain  purposes. 

575.  Distillation  of  Coal  and  Wood. — Illuminating  Gas. — Coal  and  wood 
are  subjected  to  distillation  by  heating  them  to  redness  in  large  cast-iron 
retorts,  prepared  for  the  purpose.     Usually  the  retorts  are  kept  at  a  red 
heat,  and  are  capable  of  being  opened  at  one  end,  so  that  the  charge 
may  be  changed  when  necessary. 

QUESTIONS. — What  use  is  made  of  peat?  573.  How  have  the  deposits 
of  mineral  coal  been  formed?  What  evidence  of  this  is  there  ?  574.  De- 
Bcribe  petroleum.  How  is  naphtha  obtained  from  it  ?  What  is  asphaltum, 
or  mineral  pitch  ?  575.  How  are  coal  and  wood  distilled  ? 


WOODY    FIBRE.  417 

Coal  subjected  to  this  process  gives  off  large  quantities  of  gaseous  car- 
buretted  hydrogens  (309),  with  carbonic  acid  and  sulphuretted  hydrogen, 
And  a  resinous  substance  not  unlike  tar,  called  coal-tar. 

This  last  substance  is  a  mixture  of  several  compounds,  as  naphthalene, 
phenol,  salts  of  ammonia,  &c. 

A  gas,  not  unlike  that  prepared  by  the  distillation  of  coal,  is  often 
found  to  issue,  ready  formed,  from  the  earth,  and  may  be  collected  and 
used  like  that  formed  by  art.  The  village  of  Fredonia,  in  the  State  of 
New  York,  is  lighted  by  natural  gas,  in  this  way ;  and  in  some  salt-works 
in  Virginia,  it  is  said,  no  other  fuel  is  used  for  boiling  the  brine. 

576.  Wood  by  distillation  yields  illuminating  gas  with  water,  acetic  acid, 
creosote,  pyroxylic  spirit  (methylic  alcohol],  tar,  &c.  •  The  acetic  acid,  as 
first  obtained,  is  mixed  with  creosote  and  other  substances,  and  is  called 
pyroligneous  acid. 

Creosote,  C^HjgC^,  which  passes  over,  with  other  products,  in  the  dis- 
tillation of  wood,  is  a  colorless,  transparent  liquid,  of  an  oily  consistence, 
and  retains  its  fluidity  at  — 1 7°.  It  has  a  specific  gravity  of  1  -04 ;  boils 
at  397°,  and  is  a  non-conductor  of  electricity.  It  has  a  burning  taste, 
and  its  odor  is  like  that  of  wood-smoke,  or  rather  of  smoked  meat.  It  is 
highly  antiseptic  to  meat :  the  antiseptic  virtue  of  tar,  smoke,  and  crude 
.pyroligueous  acid,  seems  owing  to  the  presence  of  creosote.  Its  name 
(from  kreas,  flesh,  and  sozein,  to  save}  was  suggested  by  this  property. 

Creosote  requires  about  80  parts  of  water  for  solution,  but  is  soluble  in 
every  proportion  in  alcohol  and  ether.  It  has  neither  an  acid  nor  alka- 
line reaction  with  test-paper,  but  combines  both  with  acids  and  alkalies. 
It  is  used  both  internally  and  externally  in  medical  practice. 

Naphthaline,  C20H8,  is  a  solid  substance,  obtained  by  distillation  from 
coal-tar.  It  is  a  white,  crystaline  solid,  which  melts  at  175°,  and  boils 
at  about  422°.  It  has  a  specific  gravity  of  1-05,  and  is  insoluble  in 
water,  but  dissolves  in  alcohol  and  ether. 

By  the  action  of  chlorine  and  bromine,  and  also  by  the  action  of  acids, 
as  the  sulphuric  and  nitric,  upon  this  substance,  various  interesting  com- 
pounds are  formed. 

Paraffine  is  sometimes  found  in  petroleum,  but  is  generally  procured 
by  the  distillation  of  wood-tar.  It  is  a  white,  waxlike  solid,  of  specific 
gravity  0-87,  which  melts  at  about  110°.  It  may  be  distilled  without 
alteration.  It  received  its  name  (parum  affinis)  from  the  circumstance 
that  it  manifests  little  affinity  for  other  substances. 

Eupione;  C6H6,  is  a  fragrant,  colorless  liquid,  obtained  by  the  distil- 
lation of  wood.  Its  specific  gravity  is  0-655,  and  its  boiling  point 
about  340°. 

Phenol  is  obtained  from  coal-tar  by  distillation.  Its  composition  is 
CjjHgOg,  in  which,  as  well  as  in  many  of  its  chemical  relations,  it  re- 

QUESTIONS. — What  are  formed  when  coal  is  distilled  ?  676.  What  com- 
pounds are  mentioned  as  being  obtained  by  the  distillation  of  wood  t 
Describe  creosote.  What  is  the*  derivation  of  the  name,  creosote  ?  Do- 
scribe  naphthaline.  Paraffine.  Eupione.  What  is  said  of  phenol  ? 


418  WINE    ALCOHOL. 

sembles  the  alcohols  (547),  and  has  therefore  been  called  phenylic  ikohol 
By  the  action  of  reagents,  many  compounds  are  formed  from  it,  analo- 
gous to  those  obtained  from  the  alcohols. 


ALCOHOLS  AND  SUBSTANCES  DERIVED  FROM  THEM. 

577.  The  name  alcohol  has  long  been  applied  to  a  well  known 
liquid,  obtained  by   fermentation  and  distillation  from  solution 
of  sugar,  and  starch,  or  substances  containing  one  or  the  other 
of  these  compounds.     But  in  the  progress  of  the  science,  several 
other  compounds,  analogous  to  common  alcohol,  both  in  compo- 
sition and  properties,  have  been  discovered,  to  which  the  name 
is  also  given.      The  general  formula,   C8MHa(n+1)Og  (545),  may 
represent  their  composition. 

The  three  most  important  of  the  alcohols  are,  common,  or  wine  alcohol, 
methylic  alcohol,  and  amylic  alcohol,  which,  with  their  derivatives,  will  be 
here  described ;  the  others  will  be  attended  to  in  their  proper  places. 

WINE    ALCOHOL,    C4H602. 

578.  Common,  or  wine  alcohol,  is  always  produced  by  the  fer- 
mentation of  sugar  or  starch,  or  compounds  containing  one  or  the 
other  of  these  substances. 

*-  579.  Fermentation. — By  the  fermentation  of  a  substance,  we 
mean  a  change  or  modification  which  takes  place  in  its  constitu- 
tion under  the  influence  of  another  substance,  called  a  ferment, 
which  acts  simply  by  its  presence. 

Several  different  fermentations  have  received  separate  names, 
as  the  vinous  or  alcoholic  fermentation,  by  which  alcohol  is  pro- 
duced from  starch  or  sugar ,  the  viscous  fermentation,  by  which 
sugar  is  converted  into  a  viscous,  or  mucilaginous  substance;  the 
acetic  fermentation,  by  which  diluted  alcohol  and  other  substances 
are  changed  to  acetic  acid,  &o. 

The  most  important  ferment  used  for  inducing  the  vinous  fermentation 
is  yeast,  or  leaven;  but  blood,  albumen,  caseine,  and  the  juices  of  many 

QUESTIONS. — 577.  Give  the  general  formula  for  the  alcohols.  Name  tho 
three  most  important  alcohols.  678.  How  is  common,  or  wine  alcohol, 
always  produced?  579.  What  is  meant  by  fermentation?  What  dif- 
ferent fermentations  are  mentioned  ?  What  ferment  is  generally  used  te 
produce  the  vinous  fermentation  ? 


WINE    ALCOHOL. 


419 


Yeast  Plant. 


fruits,  as  currants,  apples,  grapes,  &c.,  are  capable,  after  being  exposed 
for  a  time  to  the  air,  of  producing  the  same  effect. 

Yeast  is  a  substance  which  collects  as  a  froth  upon  the  surface  of  beer, 
and  other  liquids,  in  the  process  of  fermentation.  It  always  contains  a 
portion  of  nitrogen,  which  seems  essential  to  it,  but  the  mode  of  its 
action  has  not  been  determined. 

Active  yeast  is  believed  by  many  to 
contain  a  kind  of  microscopic  vegetable, 
which  is  developed  spontaneously  in  the 
organs  of  plants,  and  in  many  nitrogenized 
substances  when  left  to  putrefy.  It  can 
be  observed  only  by  use  of  the  microscope. 
See  figure  in  the  margin. 

To  induce  the  vinous  fermentation,  a 
quantity  of  sugar  is  dissolved,  or  an  equal 
quantity  of  starch  diffused,  in  4  or  6  times 
its  weight  of  water,  a  small  quantity  of 
yeast  stirred  in,  and  the  mixture  placed  in  a  situation  where  it  may 
retain  a  uniform  temperature  of  70°  to  85°.  After  a  time  the  solution 
will  be  found  in  brisk  efferves- 
cence, occasioned  by  the  escape 
of  gaseous  matter,  which  may 
easily  be  collected  over  mer- 
cury (see  figure),  and  on  ex- 
amination proves  to  be  pure 
carbonic  acid.  When  the  action 
has  ceased  the  liquid  again  be- 
comes clear,  and  is  found  to 
contain,  not  sugar,  but  alcohol, 
which  may  be  separated  by  dis- 
tillation, and  by  other  modes.  Alcoholic  Fermentation.  ^ 

In  this  way  it  is  found  that  alcohol  and  carbonic  acid  alone  are  pro- 
duced by  the  vinous  fermentation,  in  the  proportion  of  2  equivalents 
of  the  former  to  4  equivalents  of  the  latter.  It  would  not  seem  difficult, 
therefore,  to  understand  the  nature  of  the  change  that  takes  place  when, 
fruit-sugar  (560)  is  used,  for  this  sugar  contains  precisely  the  elements 
of  these  compounds  in  this  proportion.  Thus, 


C12H120, 


;2(C4H602)-f  4C02. 


But  when  starcn,  C12H10010,  cane-sugar,  C12RU01V  or  grape-sugar, 
CWH14014,  is  fermented,  the  case  is  a  little  different,  and  the  first  effect 
of  the  ferment  is  to  convert  them  into  fruit-sugar,  by  an  obvious  change. 

580.  Preparation  and  Properties, — Alcohol  obtained  by  dis- 
tillation always  contains  a  portion  of  water,  even  after  several 


QUESTIONS. — What  is  yeast?  What  is  represented  by  the  figure? 
What  are  the  products  of  the  vinous  fermentation  ?  How  many  equiva- 
lents of  alcohol  and  carbonic  acid  are  produced  from  an  atom  of  fruit- 
sugar  ?  580.  May  pure  alcohol  be  obtained  by  distillation  ? 


420  .  WINE    ALCOHOL. 

successive,  distillations.  When  most  highly  rectified  in  this 
mode,  it  contains  about  90  per  cent,  of  pure  alcohol,  the  rest 
being  water.  The  alcohol,  or  spirits  of  wine,  of  commerce  is 
seldom  as  pure  as  this.  To  obtain  absolute  alcohol,  or  alcohol  in 
a  state  of  purity,  common  alcohol  is  carefully  distilled,  by  the 
heat  of  a  water-bath,  from  pearlash  or  chloride  of  calcium,  pre- 
viously dried  and  mixed  with  it.  The  water  combines  with  the 
salt  and  remain.s  behind,  while  the'  pure  alcohol  distils  over. 

Alcohol  sufficiently  pure  for  almost  any  pur- 
pose, may  be  obtained,  without  distillation,  by 
means  of  well-dried  pearlash.  For  this  purpose, 
take  common  alcohol,  or  even  proof-spirit,  or 
Whiskey,  and  pour  into  it  half  its  weight  or  more 
of  pearlash,  which  has  previously  been  thoroughly 
dried  by  heat.  The  whole  is  then  to  be  shaken 
together  a  few  minutes,  and  allowed  to  stand 
several  hours ;  there  will  then  appear  in  the 
vessel  two  liquids  entirely  separate,  one  above 
the  other,  as  shown  in  the  figure.  The  upper 
portion  is  to  be  carefully  drawn  off  and  subjected 
to  a  second  operation  of  the  same  kind,  by  means 
of  a  fresh  portion  of  dried  pearlash ;  and  this 
Solution  of  Pearlash  in  operation  is  to  be  continued  as  long  as  the  intro- 
duction of  the  pearlash  produces  any  effect. 

Pearlash  is  soluble  in  water,  but  quite  insoluble  in  alcohol;   when, 
therefore,  a  portion  of  it,  perfectly  dry,  is  introduced  into  alcohol  con- 
taining water,  the  latter  dissolves  it,  and  the  dense  solution  settles  to  the 
bottom,  while  the  alcohol  remains  above.     After  several  repeated  opera- 
tions, all  the  water,  or  nearly  all,  is  thus  separated. 

581.  Pure  alcohol  is  a  colorless  liquid,  of  a  pungent  taste  and 
odor;  and  at  60°  has  a  density  of  0-795.  It  boils  at  172°;  and 
its  vapor  is  highly  inflammable,  and  burns  with  a  pale  yellowish 
flame,  without  smoke.  It  has  never  been  frozen  by  any  cold  yet 
produced ;  but  at  a  temperature  of  — 146°,  becomes  thick  and 
tenacious,  like  melted  wax.  It  is  -a  powerful  solvent  for  many 
substances  totally  insoluble  in  water,  especially  many  of  the 
resins.  Hydrate  of  potassa  (and  also  of  the  other  alkalies)  dis- 
solves readily  in  alcohol,  forming  a  solution  often  used  in  the 
laboratory. 

When  potassium  (or  sodium)  is  immersed  in  absolute  alcohol, 

QUESTIONS. — How  may  pure  or  absolute  alcohol  be  procured?  De- 
scribe the  mode  by  the  use  of  pearlash.  581.  Describe  the  properties 
of  alcoho1. 


WINE    ALCOHOL.  *  421 

hydrogen  is  given  off,  and  a  crystaline  compound  formed  having 
the  same  composition  as  alcohol,  except  that  1  atom  of  hydrogen 
is  replaced  by  1  atom  of  potassium.  Thus. 

C4H602  +  K  =  C4H5K02. 

By  contact  with  water,  this  compound  is  converted  into  alcohol 
and  hydrate  of  potassa. 

Vapor  of  alcohol  has  a  density,  as  determined  by  experiment,  of  1-613; 
but,  as  calculated  from  the  densities  of  its  constituents,  it  is  1-596, 
Thus, 

-    ,        4  vols.  carbon  vapor  weigh  (-836  x  4)  3-344 

12     «     hydrogen  "      (-069   Xl2)     -828 

2'    "     oxygen  "    (1-106  x  2)  2-212 

4  vols.  alcohol  vapor  weigh  6-384 

One  vol.  alcohol,  vapor  therefore  weighs  1-596. 

Alcohol  exists  in  every  kind  of  spirituous  liquors,  and  may  be  separated 
from  them  by  distillation.  The  diiferent  kinds  of  brandy,  rum,  gin,  and 
whiskey,  usually  contain  from  45  to  55  per  cent,  of  pure  alcohol ;  the 
stronger  wines  from  18  to  25  per  cent. ;  and  the  weaker,  not  more  than 
12  or  15  per  cent.  In  cider,  ale,  and  porter,  the  quantity  varies  from 
4  to  10  per  cent. 

Alcohol  is  extensively  used  in  the  arts  and 
in  medicine,  chiefly  in  consequence  of  its 
powerful  solvent  qualities.  Taken  internally, 
it  operates,  as  is  well  known,  as  a  powerful 
stimulant ;  and  various  alarming  diseases, 
often  terminating  in  extreme  moral  degra- 
dation and  death,  attend  its  habitual  use. 

Used  in  lamps  instead  of  oil,  great  heat  is 
produced,  and  the  combustion  is  unattended 
with  smoke,  for  which  reason  it  is  much  em- 
ployed  in  the  laboratory.  A  cover,  a,  fitting 
accurately  upon  b,  prevents  evaporation  when 
not  in  use.  Spirit-lamp. 

582.  Bread-making. — The  ordinary  mode  of  raising  bread  by  means 
of  yeast,  also  furnishes  an  instance  of  the  vinous  fermentation.  The 
yeast  contained  in  the  flour-paste,  or  dough,  causes  the  fermentation  to 
commence,  as  already  explained,  and  both  alcohol  and  carbonic  acid  are 
formed  in  the  dough ;  arid  the  latter  being  retained  in  the  tenacious  mass 
causes  it  to  swell  up,  or  rise.  This  effect  is  further  increased  by  the 
expansion  of  the  gas  by  the  heat  in  the  process  of  baking,  giving  the 

QUESTIONS. — What  is  the  effect  when  potassium  is  immersed  in  alco- 
hol ?  In  what  is  alcohol  always  contained  I  682.  What  is  said  of  bread- 
making  ? 

36  - 


422  »          WINE    ALCOHOL. 

bread  its  light,  porous  character.     The  small  quantity  of  alcohol  formed 
is  dissipated  by  the  heat  of  the  oven. 

Bread  is  also  raised,  as  is  well  known,  by  the  use  of  bicarbonate  of  soda, 
or  potash,  and  an  acid,  as  the  hydrochloric  or  tartaric  acid,  or  the  acid 
tartrate  of  potash  (cream  of  tartar).  The  rising  is  in  this  case  produced 
by  carbonic  acid  liberated  in  the  dough  from  the  alkaline  carbonate ;  and 
the  same  light,  spongy  character  given  to  the  bread. 


Products  of  the  Oxydation  of  Wine  Alcohol. 

583,  Aldehyde,  C4H402.  —  Aldehyde  (from  alcohol  dehydro- 
genatus),  as  will  be  seen  by  an  inspection  of  its  formula,  is 
dehydrogenated  alcohol,  —  alcohol  from  which  two  atoms  of 
hydrogen  have  been  separated.  The  separation  of  the  hydrogen 
is  effected  by  distilling  alcohol  with  highly  oxydized  substances, 
which  readily  give  up  a  portion  of  their  oxygen  to  form  water 
with  the  eliminated  hydrogen. 

The  best  method  for  preparing  it,  is  to  mix  in  a  retort  equal 
parts  of  powdered  bichromate  of  potash  and  strong  alcohol,  and 
then  add,  in  successive  portions,  1J  parts  of  sulphuric  acid. 
Energetic  action  commences  at  once,  much  carbonic  acid  is  given 
off,  and  aldehyde,  mixed  with  a  small  quantity  of  acetic  acid  and 
other  substances,  distils  over  into  the  receiver,  which  is  kept 
surrounded  with  ice.  To  the  liquid  thus  obtained,  some  ether  is 
added,  and  it  is  then  saturated  with  ammonia,  which  forms  with 
aldehyde  a  crystaline  compound,  aldehyde  ammonia,  NH3,C4H402. 
This  solid,  distilled  at  a  gentle  heat  with  dilute  sulphuric  acid, 
and  then  re-distilled  from  chloride  of  calcium,  previously  fused, 
affords  the  pure  aldehyde. 

Aldehyde  is  a  colorless  liquid,  of  a  peculiar  suffocating  odor; 
at  60°  its  density  is  0-790,  and  it  boils  at  the  low  temperature 
of  70°  or  71°.  It  is  soluble  in  water,  alcohol  and  ether;  and 
burns  with  a  pale  flame.  It  dissolves  sulphur,  phosphorus,  and 
iodine ;  and  is  especially  remarkable  for  its  affinity  for  oxygen, 
in  consequence  of  which  it  is  capable  of  reducing  many  of  the 
metallic  salts.  Its  action  upon  nitrate  of  silver  is  remarkable. 
If  a  solution  of  this  salt  is  poured  into  a  clean  glass  vessel,  with 

QUESTIONS. — What  occasions  the  rising  which  gives  to  bread  its  spongy 
character?  583.  What  is  aldehyde?  Describe  the  mode  of  preparing 
it.  What  are  some  of  its  properties  ? 


WINE    ALCOHOL.  423 

a  little  ammonia,  the  addition  of  some  water,  mixed-  with  alde- 
hyde, causes  an  immediate  precipitation  of  the  silver  upon  the 
surface  of  the  glass,  which  retains  its  perfect  metallic  lustre,  like 
the  coating  of  a  looking-glass. 

Aldehyde  is  instantly  decomposed  by  contact  with  an  alkali ;  and  if 
kept  only  a  short  time,  it  changes  spontaneously  into  one  or  two  other 
compounds  isomeric  with  itself,  depending  upon  the  temperature ; — these 
are,  daldehyde  and  metaldehyde,  the  former  of  which  is  liquid  and  the 
latter  solid.  By  combining  with  oxygen,  aldehyde  forms  aldehydic  or 
acetous  acid,  C4H403. 

581  Acetic  Acid,  C4H404==C4H303JHO.— Acetic  acid  is  well 
known  as  the  acid  contained  in  vinegar  (from  the  French  vin, 
wine,  and  aigre,  sour),  which  is,  in  fact,  a  very  dilute  acetic  acid, 
containing  also  much  saccharine  and  mucilaginous  matter.  Acetic 
acid  is  one  of  the  most  important  of  the  organic  acids,  and  is 
found,  in  combination  with  bases,  in  many  plants. 

This  acid  is  formed  artificially  by  a  variety  of  processes,  but 
the  usual  method  of  preparing  it  is  to  subject  liquids  containing 
alcohol,  as  the  weaker  wines,  cider,  &c.,  to  the  action  of  some 
ferment,  while  exposed  to  the  atmosphere.  The  process  has 
sometimes  been  called  the  acetic  fermentation ;  and  the  chemical 
changes  which  take  place  in  it  consist  in  the  separation  from  the 
alcohol  of  2  atoms  of  hydrogen  by  the  oxygen  of  the  air,  forming 
aldehyde  and  water,  and  the  subsequent  absorption  of  2  additional 
atoms  of  oxygen  by  the  aldehyde.  Thus, 

C4H602  +  20  =  C4H402  +  2  HO,  and 
C4H402  +  20  =  C4H404. 

•The  access  of.  atmospheric  air  is  absolutely  es- 
sential to  the  formation  of  vinegar  by  the  ordinary 
process,  as  is  well  known ;  and  its  production  is 
much  facilitated  by  a  method  invented  in  Germany. 
A  cask,  as  shown  in  the  figure,  is  filled  with  wood 
shavings,  and  closed  at  top  by  a  pan,  b,  the  bottom 
of  which  is  perforated  with  many  small  holes, 
through  which  small  threads  are  passed  to  conduct 
the  liquid  downward.  The  shavings,  being  first 
well  soaked  in  vinegar,  are  placed  lightly  in  the 
cask;  and  below  them  are  several  small  holes,  cc, 
about  half  an  inch  in  diameter,  to  admit  the  free  Prep,  of  Vinegar. 

QUESTIONS. — Can  aldehyde  be  kept  without  change?  584.  What  is 
vinegar?  How  is  it  formed  artificially  ?  Describe  the  German  process. 


424 


WINE    ALCOHOL. 


accession  of  air.  If  now  proof-spirit,  diluted  with  four  times  its  weight 
of  water,  and  having  mixed  with  it  a  very  little  honey  or  yeast,  is  poured 
into  the  pan  above,  it  gradually  trickles  down  upon  the  shavings,  where, 
a  large  surface  being  exposed  to  the  atmosphere,  rapid  absorption  of 
oxygen  takes  place,  the  temperature  is  raised,  and  acetic  acid  is  formed. 
As  the  liquid  passes  down,  it  is  collected  in  the  vessel  a ;  and  when 
passed  through  three  or  four  times,  which  requires  but  about  36  hours, 
it  is  converted  into  vinegar. 

Acetic  acid  .cannot  be  separated  from  water  by  mere  distillation ;  but 
the  pure  acid  is  obtained  by  distilling  some  acetate,  as  acetate  of  soda 
or  lime,  &c.,  with  a  proper  quantity  of  sulphuric  acid,  and  collecting  the 
product  in  a  cold  receiver. 

Wood-vinegar,  or  pyroligneous  acid,  is  obtained  by  distilling  wood  in 
close  vessels.  It  is  a  very  impure  acetic  acid,  having  a  disagreeable, 
smoky  odor,  and  containing  empyreumatic  oils,  and  other  substances 
derived  from  the  wood.  It  is  much  used  in  calico-printing ;  and  often 
the  cloths,  not  having  been  properly  cleansed,  possess  its  disgusting 
odor. 

585.  Pure  acetic  acid,  at  63°,  is  a  colorless  liquid,  of  a  pungent, 
refreshing  odor,  and  excessively  sour  to  the  taste.     Applied  to 
the  skin  for  a  time,  it  produces  blisters.     It  boils  at  248° ;  and 
cooled  below  63°,  it  may  be  obtained  in  crystals.     At  63°,  the 
density  of  the  liquid  is  1-06.     It  mixes  readily  with  water,  ether, 
or  alcohol. 

586.  Acetal,  C12HM03. — This  compound  is  a  clear,  colorless 

liquid,  which  boils  at  about  167°,  and  has 
a  density  of  0-844.  It  is  formed  by  the 
•slow  action  of  moistened  platinum  black 
upon  a  mixture  of  vapor  of  alcohol  and 
oxygen,  in  a  large  bell-glass.  The  bell- 
glass  is  to  be  open  at  top,  and  elevated 
a  little  from  the  bottom  of  the  basin  in 
which  it  is  placed,  as  represented  in  the 
figure,  so  as  to  allow  a  gradual  circulation 
of  the  air  through  it.  A  watch-glass,  A, 
is  placed  in  the  centre  of  the  basin,  contain- 
ing a  little  platinum  black;  and  a  small 
Prep,  of  Acetal.  ,  funnel,  with  a  long  neck,  B,  contains  strong 
alcohol,  which  drops  very  slowly" into  the  watch-glass.  By  the 


QUESTIONS. — What  is  pyroligneous  acid  ?     585.  Describe  the  properties 
of  pure  acetic  acid.     686.  How  is  acetal  formed  ? 


WINE    ALCOHOL.  425 

catalytic  action  of  the  platinum,  the  alcohol  is  decomposed,  and 
acetal,  aldehyde,  and  acetic  acid,  are  formed,  and,  condensing 
together  upon  the  sides  of  the  bell-glass,  are  collected  in  the 
basin.  This  liquid  is  now  to  be  neutralized  with  powdered 
chalk,  and  carefully  distilled  from  chloride  of  calcium. 

Salts  of  Acetic  Acid,  and  Other  Allied  Compounds. 

587.  Acetic   acid   combines  with   most   bases,  forming   salts 
called  acetates.      In    combination,  its    composition    is   C4H303; 
from  which  it  appears   that  in   the   process  of  combining,  one 
atom  of  water — or  the  elements  of  water — is  given  up.     Or,  we 
may  consider  (with  some  chemists)   the  metal  of  the  base  as 
simply  replacing  1  equivalent  of  the  hydrogen  of  the  acid  (353). 
Thus,  when  acetic  acid  combines  with  soda,  the  acetate  of  soda 
formed  has  for  its  composition,  NaO,  C4H303 ;  and  we  may  indi- 
cate the  supposed  relationship  of  the  sodium  as  replacing  1  equiva- 
lent of  the  hydrogen  of  the  acid  by  writing  its  formula  thus, 
C4II3(Na)04. 

Acetic  acid  is  monobasic ;  that  is,  the  salts  it  forms  contain  a  single 
equivalent  of  the  acid  with  one  equivalent  of  base.  These  salts  are  also 
said  to  be  monobasic  (170,  349). 

We  shall  describe  only  a  few  of  the  more  important  acetates. 

588,  Acetate  of  Lead,  PbO,C4H303  +  3HO.—  This  is  the 
sugar  of  lead  of  commerce.     It  is  formed  by  dissolving  oxide 
of  lead  (litharge)  in  acetic  acid.     It  is  very  soluble  in  pure  water, 
and  has  a  sweet,  astringent  taste.     Taken  internally,  it  is  poi- 
sonous;  but  is  used  in  various  preparations  in  medicine.     The 
3  HO  is  water  of  crystalization. 

If  we  consider  the  metal  as  replacing  an  equivalent  of  the 
hydrogen  of  the  acid,  its  formula  may  be  written,  C4H3(Pb)04. 

Besides  the  above  neutral  acetate  of  lead,  there  are  several  other 
acetates  of  the  same  base,  which  are  formed  by  the  combination  of  this 
compound  with  additional  equivalents  of  oxide  of  lead,  as  2PbO,3C4H3Os, 
and  3PbO,C4H803.  The  latter  of  these,  sometimes  called  tribasic  acetate 
of  lead,  is  used  in  medicine,  and  in  the  proximate'analysis  of  organic 

QUESTIONS. — 587.  What  are  the  salts  of  acetic  acid  called?  What  is 
said  .of  acetic  acid  as  it  combines  with  bases  ?  Is  this  acid  monobasic  ? 
What  is  meant  by  this  ?  588.  Describe  acetate  of  lead.  What  is  it 
called  in  commerce? 

36* 


426  WINE    ALCOHOL. 

compounds.  It  is  formed  by  digesting  7  parts  of  litharge  iit  <.  parts 
of  the  neutral  acetate  in  30  parts  of  water,  and  evaporating  tiie  Solution 
until  crystals  are  formed  on  cooling.  The  solution  is  called  in  pharmacy 
Goulard's  extract  of  lead. 

589.  Acetate  of  Copper,  CuO,C4H303. — Acetate  of  copper  is 
obtained  by  dissolving  verdigris  in  hot  acetic  acid.     On  cooling, 
it  is  obtained  in  fine  green  crystals,  yMch  contain  one  atom  of 
water,  and  is  sometimes  called  distilled  verdigris.     This  salt  i 
capable  of  uniting  with  additiona'  equivalents  of  oxide  of  copper, 
forming  sub-acetates ;  and  the     erdigris  of  commerce,  used  as  a 
paint,  appears  to  be  a  mixtirjj  of  these.     It  is  prepared  in  large 
quantities,  in  the  south  of,  France,  by  covering  copper  with  the 
refuse  of  grapes,  after  tLe  juice  has  been  extracted  for  making 
wine ;   the  saccharinp   matter  contained  in  the  husks  furnishes 
acetic  acid  by  fermentation,  and  in  four  or  six  weeks  the  plates 
acquire  a  coating  of  the  acetate.     A  purer  and  better  article  is 
prepared  by  covering  copper  plates  with  cloths  soaked  in  pyro- 
ligneous  acid 

590.  Acef  /.a  of  Ah?m?na,  Ab203,3(C4H303). — This  salt  is  prepared  by 
decomposing  solution  of  sugar  of  lead  by  alum.     It  is  used  in  dyeing, 
and  calico  -printing. 

591.  Acetate  of  Iron. — By  treating  iron-filings  with  dilute  acetic  acid, 
a  mixture  of  the  acetates  of  the  proto  and  sesquioxides  of  iron  is  obtained, 
which  is  considerably  used  in  the  arts. 

592.  Acetate  of  Ammonia,  NH3,C4H303,HO  =  C4H3(NH4)04,  is  readily 
formed  by  neutralizing  acetic  acid  with  ammonia,  or  its  carbonate.     It 
has  been  used  in  medicine  under  the  name  of  spirit  of  Mindererus. 

593.  ChloraceticAcid,  C4H04Cl3=:C4Cl303,HO,orC4H(C]3)04. 
— This  acid  is  formed  from  acetic  acid,  by  the  abstraction  of  3  atoms 
of  its  hydrogen,  and  the  substitution  of  3  atoms  of  chlorine.     It  is 
prepared  by  placing  some  crystals  of  acetic  acid  under  a  large  bell- 
glass  filled  with  chlorine,  and  exposing  it  to  the  direct  rays  of  the 
sun.     Other  compounds  are  formed  at  the  same  time,  which  are  to 
be  separated  from  it,  and  then  it  is  obtained  in  colorless  rhomboidal 
crystals. 

QUESTIONS. — 589.    How  is  acetate  of  copper  formed?      What  is  the 
verdigris  of  commerce  ?     How  is  verdigris  prepared  ?     590.  What 
acetates  are  mentioned  ?     593.  How  is  chloracetic  acid  formed  ? 


WINE    ALCOHOL.  427 

Neglecting  the  secondary  compounds  formed,  the  reactions  will 
be  represented  as  follows,  viz.  : 

C4H303,HO  +  6C1  =  C4C1303,HO  4  3HC1. 

The  crystals,  when  heated,  melt  at  113°,  and  the  liquid  boils  at 
about  392°.  It  closely  resembles  acetic  acid  in  its  properties, 
neutralizes  the  same  quantity  of  bases,  and  forms  salts  similar  to 
the  acetates. 

594.  Acetone,  C6H602.  —  Acetone,   or  pyroacetic  spirit,  is  a 
limpid  liquid,  obtained  by  passing  vapor  of  acetic  acid  through  a 
red-hot  tube,  or  by  distilling  a  mixture  of  dry  sugar  of  lead  and 
powdered  quicklime,  and  condensing  the  product  in  a  cool  receiver. 
Much  uncondensable,  gaseous  matter  passes  over  at  the  same  time, 
which  is  allowed  to  escape.     It  has  a  density  of  0*792,  and  boils 
at  132°.     In  some  of  its  properties,  acetone  appears  to  be  closely 
allied  to  the  alcohols,  but  in  its  composition  it  is  isomeric  with 
the  aldehyde  of  propylic  alcohol  (547). 

In  the  preparation  of  acetone,  another  allied  compound  often  makes 
its  appearance,  called  metacetone,  or  propione,  C6H60.  (We  should  prefer 
to  call  it  propylone.}  A  corresponding  acid  is  known,  called  the  metace- 
tonic,  propionic,  or  propylic  acid,  C6H604. 

Action  of  Chlorine  upon  Alcohol. 

595.  When  a  current  of  dry  chlorine  is  passed  through  anhydrous 
alcohol,  the  first  effect  is  to  produce  aldehyde  and  hydrochloric  acid. 
Thus, 

C4H602  +  2C1  =  C4H402  +  2HC1. 


Two  equivalents  of  chlorine,  therefore,  have  separated  2  eq.  of  the 
hydrogen  of  the  alcohol,  forming  2  eq.  of  hydrochloric  acid,  the  residue 
of  the  alcohol  constituting  aldehyde. 

But  if  the  action  of  the  chlorine  is  continued,  a  new  compound  is 
formed,  called  chloral,  C4HC1302.  It  may  be  regarded  as  aldehyde  in 
which  3  eq.  of  hydrogen  have  been  replaced  by  3  eq  of  chlorine.  The 
reactions  are  as  follows  : 

C4H402  4.  601=  C4HC1302  4-  3HC1. 
Or,  regarding  it  from  the  beginning  of  the  process,  ^ 
C4II602  4  8C1  =  C4HC1302  4  5HC1. 

QUESTIONS.  —  594.  Describe  the  mode  of  preparing  acetone.  695.  What 
is  the  first  effect  when  dry  chlorine  is  passed  through  pure  alcohol?  What 
is  formed  when  the  process  is  continued  ?  How  may  chloral  be  regarded? 


428  METHYLIC    ALCOHOL. 

Chloral  is  an  oily  liquid,  of  specific  gravity  1-5,  which  boils  at  201°, 
and  has  a  strong  affinity  for  water,  being  soluble  in  water,  alcohol,  or 
ether. 

METHYLIO    ALCOHOL,     OR    WOOD -SPIRIT,     C2H402. 

596,  Preparation  and  Properties, — When  wood  is  subjected 
to  distillation  in  a  close  vessel,  besides  the  uncondensable  gases 
which  pass  over,  there  is  obtained  an  aqueous  liquid,  composed 
of  pyroligneous  acid  (584),  and  other  compounds ;  among  which, 
is  a  volatile,  inflammable  liquid,  long  known  as  wood-spirit,  or 
pyroxylic  spirit  (from  pur,  fire,  and  xulon,  wood).  But  from  its 
resemblance  to  alcohol,  in  composition  (547)  and  many  of  its 
properties,  it  is  more  properly  designated  as  methylic  alcohol, 
(from  methuj  wine,  and  xulon,  wood). 

To  separate  it  from  the  other  compounds,  the  crude  liquid  is 
first  neutralized  with  lime,  and  carefully  distilled,  only  the  part 
that  passes  over  first  being  preserved,  as  this  will  contain  nearly 
the  whole  of  the  wood-spirit.  To  obtain  it  pure,  it  must  be  several 
times  re-distilled  from  chloride  of  calcium  and  lime. 

Metbylic  alcohol  is  a  colorless  liquid,  with  an  odor  and  taste 
somewhat  resembling  those  of  common  alcohol.  It  has  a  density 
of  0-798,  and  boils  at  152°,  and  burns  freely  in  a  lamp. 

It  mixes  readily  with  water,  alcohol,  and  ether,  and,  like  com- 
mon alcohol,  dissolves  freely  most  resinous  substances.  Some  use 
has  been  made  of  it  in  the  treatment  of  diseases,  under  the  name 
of  wood  naphtha. 

The  formula  of  this  compound,  C2H402,  represents  4  vols.  of  its  vapor, 
the  density  of  which,  by  calculation,  is  1-109,  as  follows: 

2  vols.  carbon  vapor  weigh         (-836  x  2)         1-672 
8  vols.  hydrogen,  (-069  x  B)  -552 

2  vols.  oxygen,  (1-106  x  2)         2-212 

Giving  for  4  vols.  vapor  of  methylic  alcohol,  4-436 
The  weight  of  1  vol.,  or  density,  therefore,  is  1-109 

Products  of  the  Oxyclation  of  Methylic  Alcohol. 

597.  Formic  Acid,  C2H204  =  C2H03,HO.— This  acid  was  first 
obtained,  by  distillation,  from  the  bodies  of  red  ants  (^formica 

QUESTIONS. — 596.  From  what  is  methylic  alcohol,  or  wood-spirit,  ob- 
tained ?  Describe  methylic  alcohol.  597.  From  what  was  formic  acid 
first  obtained  ? 


METHYLIC    ALCOHOL. 


429 


rufa) ;  and  hence  its  name.  Its  relation  to  methyhc  alcohol  is 
the  same  as  that  of  acetic  acid  to  common  alcohol.  It  may  be 
obtained  by  exposing  the  vapor  of  wood-spirit,  mixed  with  air,  to 
the  action  of  platinum  black,  under  a  receiver,  water  and  formic 
acid  being  produced  at  the  same  time.  It  appears  that  two  atoms 
of  oxygen  combine  with  2  atoms  of  the  hydrogen  of  the  spirit, 
forming  2  atoms  of  water;  and  then  2  atoms  more  of  oxygen 
unite  with  the  residue  to  form  the  acid.  Thus, 

C2H402  +  20  =  C2H202  +  2HO,  and 
C2H202  +  20  =  C2H204. 

Formic  acid  may  also  be  produced  by  distilling  a  mixture  of 
sugar,  bichromate  of  potash,  and  oil  of  vitriol,  and  by  other 
means. 

Formic  acid  is  .a  clear  liquid,  of  specific  gravity  1-24,  has  a 
strong  acid  taste  and  pungent  odor,  and  quickly  blisters  the  skin. 
It  boils  at  212°,  producing  an  inflam- 
mable vapor,  and  solidifies  at  about 
32°.  It  is  contained  in  small  quan- 
tities in  many  plants,  as  the  nettle, 
and  produces  the  pain  occasioned  by 
handling  them.  The  figure  repre- 
sents the  "sting"  of  the  nettle,  greatly 
magnified,  with  the  sacks  at  the  base 
containing  the  acid. 

When  this  acid  combines  with 
bases,  like  acetic  acid,  it  gives  up 
the  elements  of  an  atom  of  water; 
and  is  therefore  by  many  considered 
as  a  hydrate,  and  its  formula  written 
C2H03  +  HO.  Or,  as  in  the  case  of 
acetic  acid  (587),  we  may  consider  the  metal  of  the  base  as 
replacing  1  equivalent  of  the  hydrogen  of  the  acid.  Thus,  the 
forrniate  of  lead,  PbO,C2H03,  on  this  supposition,  will  have  for 
its  formula,  C2H(Pb)04.  It  is  monobasic,  like,  acetic  acid. 

QUESTIONS. — What  is  said  of  the  relation  of  formic  acid  to  methylic 
alcohol?  May  it  be  procured  from  sugar ?  Describe  the  process.  De- 
scribe its  properties.  Is  it  found  in  plants  ?  What  is  said  of  the  nettle  ? 


Sting  of  Nettle. 


430  AMTLIC    ALCOHOL. 

598.  The  formiaies,   in  their  general  properties,   resemble  the  cor- 
responding  acetates.     The  alkaline  formiates  are  used  in  the  analyses 
of  some  minerals. 

599.  Methylal,  C6H804.  —  This  substance  is  procured  by  distilling  a 
mixture,  in  proper  proportion,  of  methylic  alcohol,  dilute  oil  of  vitriol, 
and  peroxide  of  manganese,  and  purifying  the  product.     It  is  a  colorless 
liquid,  of  an  agreeable  aromatic  odor,  and  burns  with  a  yellow  flame.     It 
has  a  density  of  0-85,  and  boils  at  108°. 


AMYLIC    ALCOHOL,        ,01202. 

600.  Amylic  alcohol  is  a  peculiar  oily  substance,  which  is  col- 
lected in  the  process  of  distilling  spiri*  from  potatoes.  It  is 
supposed  to  be  formed  from  the  starch  (amylum)  of  the  potato, 
and  hence  its  name.  It  is  also  called  potato  oil,  and  fusel  oil. 
It  is  found  in  some  kinds  of  brandy,  and  in  other  spirituous 
liquors,  being  probably  formed  during  the  fermenting  process, 
in  circumstances  not  well  understood. 

In  distilling  spirit  from  potatoes,  it  is  particularly  abundant 
towards  the  close  of  the  process  ;  it  is  then  mixed  with  water,  to 
which  it  gives  a  milky  appearance,  but  after  standing  for  a  time 
it  rises  to  the  surface. 

Amylic  alcohol  is  a  clear,  colorless  liquid,  insoluble  in  water, 
but  very  soluble  in  alcohol  and  ether.  Its  density  is  0-82,  and 
it  boils  at  270°.  Its  taste  and  smell  are  burning  and  pungent. 
If  its  vapor,  mixed  with  air,  is  breathed  for  a  little  time,  asthmatic 
pains  and  coughing  are  likely  to  ensue,  and  even  vomiting. 

It  dissolves  phosphorus,  sulphur,  and  iodine,  without  change  ; 
and,  unlike  wine  alcohol,  is  congealed  by  a  temperature  of  —  4°. 

The  formula  of  amylic  alcohol,  C10H,202,  answers  to  4  vols.  of  the  sub- 
Btance  in  the  gaseous  state.  The  calculated  density  of  its  vapor  is  3-057. 
Thus, 

10  vols.  carbon  vapor  weigh       (-836  x  10)        8-360 

24     «    hydrogen  "  (-069  X  24)        1-656 

2     "     oxygen  "          (1-106  x     2)        2-212 

Thus,  4  vols.  amylic  alcohol  vapor  weigh  12-228 

The  weight  of  1  vol.,  or  the  density,  is  therefore  3-057 

_  _     «          ___  _  _     __ 

QUESTIONS.  —  598.  What  do  the  formiates  resemble  in  their  general 
properties  ?  599.  Describe  methylal.  600.  From  what  is  amylic  alcohol 
obtained  ?  Describe  its  properties.  When  its  vapor,  mixed  with  air,  is 
breathed,  what  is  the  effect  ? 


AMYLIC    ALCOHOL.  431 


Product  of  the  Oxydation  of  Amylic  Alcohol. 

601,  Valerianic  Acid,  C10HJ004  =  C10H903,HO.  — This  acid 
sustains  the  same  relation  to  amylic  alcohol  as  acetic  acid  sustains 
to  wine  alcohol,  or  formic  acid  to  methylic  alcohol.     It  is  con- 
tained  in    the   valerian    root   (yaleriana   officinalis'),   which   is 
extensively  used  in  medicine,  and  is  obtained  by  distilling  the 
root  with  water.     It  is  also  formed  artificially  by  dropping  warm 
potato  oil  upon  platinum  black  in  contact  with  atmospheric  air, 
or  by  distilling  a  mixture  of  amylic  alcohol,  sulphuric  acid,  and 
bichromate  of  potash. 

In  the  process  of  its  formation  from  amylic  alcohol,  the  same 
chemical  changes  are  required  as  in  the  formation  of  acetic  acid 
from  wine  alcohol ; — the  alcohol  loses  2  eq.  of  hydrogen,  which 
combine  with  oxygen,  forming  water,  and  then  2  eq.  additional 
of  oxygen  are  absorbed.  Thus, 

C10HI202  +  20  =  C10H1(A  +  2HO,  and 
C10H1002  +  20  =  C10H1204. 

Pure  valerianic  acid  is  a  colorless,  oily  liquid,  of  specific  gravity 
0*937.  Its  taste  is  pungent  and  acid,  and  its  odor  like  that  of 
valerian.  Its  boiling  point  is  347°.  It  is  little  soluble  in 
water,  but  dissolves  freely  in  alcohol  and  ether.  It  combines 
with  bases,  forming  salts  in  many  respects  similar  to  the  acetates 
and  formates.  When  it  enters  into  combination,  it  gives  up  the 
elements  of  1  equivalent  of  water,  precisely  like  the  acetic  and 
formic  acids,  and  is  therefore  monobasic. 

Some  of  the  valerianates,  especially  valerianate  of  zinc,  are  used 
in  medical  practice,  as  a  substitute  for  the  preparation  of  the 
valerian  root. 

602.  Amylic  aldehyde,   C]0H,002,  analogous  to  the  aldehyde  of  wine 
alcohol,  is  formed  by  distilling  valerianate  of  baryta. 

QUESTIONS. — 601.  From  what  is  valerianic  acid  obtained?  How  may 
it  be  formed  artificially  ?  What  is  said  of  the  chemical  changes  which 
take  place  in  its  formation  ?  Describe  its  properties.  What  salt  of  this 
acid  is  used  in  medical  practice  ?  602.  How  is  amylic  alcohol  obtained? 


432  SULPHUR    ALCOHOLS. 

The  three  alcohols  above  described  are  the  most  important  of  this 
homologous  series  (547),  but  six  others  are  known,  which  will  be  here- 
after described.  These  all  have  the  formula,  C2?iH2(n+  j)02,  as  we  have 
before  (545)  seen. 

Some  other  compounds,  similar  in  their  properties  to  the  above,  but 
not  strictly  homologous  with  them,  have  been  denominated  alcohols,  as 
phenylic  alcohol,  C^HgO^  and  acrylic  alcohol,  C6H602. 


SULPHUR.  ALCOHOLS,  OR  MERCAPTANS. 

603.  These  compounds  are  formed  on  the  same  type  as  the 
alcohols,  but  differ  from  them  by  containing  sulphur  instead  of 
oxygen.  They  are  called  mercaptans  (mercurium  captans),  be- 
cause of  their  great  affinity  for  mercury,  with  which  they  eagerly 
combine,  on  coming  in  contact  with  its  oxide. 

Wine-alcohol  Mercaptan,  C4H6S2— C4H6S,HS.  —  This  com- 
pound is  formed  by  saturating  a  solution  of  caustic  potash,  of 
density  1-3,  with  sulphuretted  hydrogen,  and  distilling  it  with  an 
equal  measure  of  sulphovinate  of  lime  (a  substance  to  be  here- 
after described,)  of  the  same  density.  It  is  a  colorless  liquid, 
which  has  a  specific  gravity  of  about  0-84,  and  boils  at  97°.  Its 
odor  resembles  that  of  onions. 

Mercaptan  vapor  has  a  density  of  2-152,  as  may  be  thus  calculated: 

4  vols.  carbon  vapor  weigh         (-836  X  4)       3-344 

12  vols.  hydrogen  "      '"  (-069    Xl2)         '-828 

£  vol.  sulphur      "         "  (6-654  X   I)       4-436. 

4  vols.  mercaptan  vapor  8-608 

The  density  therefore  is,  or  the  weight  of  1  vol.,  2-152 

By  the  action  of  this  compound  upon  metallic  oxides,  1  equiva- 
lent of  its  hydrogen  unites  with  the  oxygen  of  the  oxide,  forming 
water,  and  the  metal  takes  the 'place  of  the  hydrogen  in  the  ori- 
ginal compound.  Thus,  by  the  action  of  mercaptan  on  oxide 
of  lead,  PbO,  we  have — 

C4H6S2 + PbO=C4H5S,PbS  +  HO=C4H5PbS2  +  HO. 

These  metallic  compounds,  of  which  several  more  are  known, 
are  called  mercaptides. 

QUESTIONS. — Are  there  other  alcohols  besides  the  three  described 
above?  603.  What  are  the  mercaptans,  or  sulphur  alcohols?  Describe 
wine  alcohol  mercaptan.  What  are  the  compounds  of  this  substance  with 
the  metals  called  ? 


ETHERS.  433 

as  are 


The  compound,  C4H4S2,  called  mercaplan  aldehyde,  is  known, 
also  methylic  mercaptan,  C2H4S2,  and  amylic  mercaptan,  C10H,2S2. 

Selenium  may  be  made  to  replace  the  sulphur  in  the  commoa  alcohol 
uiercaptans,  forming  seleno-mercaplans. 


ETHERS.  —  COUPLED,     OR    VINIC    ACIDS. 

604.  The  substance  usually  designated  by  the  simple  term, 
ether,  is  a  compound  obtained  by  the  reciprocal  action  of  alcohol 
and  acids,  as,  the  sulphuric,  phosphoric,  or  arsenic,  or  the 
chlorides  of  zinc,  tin,  &c.  It  is  often  called  sulphuric  etherj 
from  the  circumstance  that  sulphuric  acid  is  generally  used  in  its 
preparation.  The  name  ether,  given  to  it,  indicates  its  volatility. 

-But  the  term  is  now  extended  to  a  very  numerous  class  of 
similar  compounds,  most  of  which  are  liquid  at  ordinary  tempera- 
tures, and  are  very  volatile,  but  differ  from  each  other  as  to  the 
temperature  at  which  ebullition  takes  place.  Some  few  of  them 
are  solid. 

There  are  several  families  of  ethers  derived  from  the  several 
alcohols;  and  in  naming  them,  except  in  the  case  of  those  be- 
longing to  the  common  alcohol  group,  the  family  or  group  is 
usually  indicated.  Thus  we  have  hydrochloric  ether,  methylic 
hydrochloric  ether,  and  amylic  hydrochloric  ether ;  the  first  of 
which  belongs  to  the  wine  alcohol  group,  but  the  others  to  the 
groups  severally  indicated. 

And  in  each  alcohol  series,  there  are  also  two  distinct  classes 
of  ethers,  which  we  may  call  simple  ethers,  and  compound  ethers. 
The  former,  or  simple  ethers,  have  the  general  formula,  C2nH2n+1A 
(the  Greek  letter  A  being  used  to  indicate  one  equivalent  of  any 
one  of  the  elements,  oxygen,  chlorine,  bromine,-  iodine,  fluorine, 
sulphur,  -selenium,  tellurium,  or  a  compound  radical,  cyanogen, 
bisulphide  of  carbon,  &c.,)  while  the  compound  ethers  always 
contain  an  acid  in  combination  with  a  simple  ether,  C2nH2n+,A. 
Thus,  common  sulphuric  ether  is  a  simple  ether,  C4H50;  but 

QUESTIONS. — 604.  How  is  the  compound  usually  called  ether  obtained  ? 
Why  is  it  often  called  sulphuric  ether  ?  How  is  the  name  ether  now  used  ? 
Do  the  different  alcohols  afford  ethers  ?  What  two  classes  of  ethers  are 
there  in  each  alcohol  aeries  ?  In  what  do  the  individuals  of  the  two 
classes  differ  ? 

37 


484  ETHERS. 

nitric  ether  is  a  compound  ether  having  the  formula,  C4H6NOa  =* 
C4H60,N05. 

There  are  some  simple  ethers  which  contain  more  than  one 
equivalent  of  A ;  and  in  both  the  simple  and  compound  ethers, 
one  or  more  equivalents  of  the  hydrogen  may  be  replaced  by 
chlorine  (and  possibly  other  elements),  as  in  the  chlorocarbonio 
ether,  C4H3C120,C02. 

Ethers  of  Wine  Alcohol. 

I.     SIMPLE    ETHERS. 

605.  Ether  (Sulphuric  Ether),  C4H50.  —  This  ether  may  be 
formed  by  several  modes ;   but  the  best  is  to  distil  a  mixture  of 
equal  parts  of  alcohol  and  strong  sulphuric  acid  in  a  glass  retort, 
the  process  being  discontinued  as  soon  as  the  mixture  begins  to 
become  colored.     For  distilling  it,  an  alembic  or  other  distilling 
apparatus  (48)  may  be  used. 

The  product  should  be  washed  with  water,  to  separate  a  little  alcohol 
and  sulphurous  acid  that  usually  pass  over  with  the  ether.  This  is  done 
by  filling  a  bottle  about  half  full  with  the  impure  ether,  and  then  pouring 
in  a  quarter  or  one-half  as  much  water,  and  shaking  them  well  together. 
After  standing  a  few  minutes,  the  liquids  separate,  and  the  water  may 
be  drawn  off  by  perforating  the  cork  and  inverting  the  bottle,  taking 
care  to  notice  when  the  water  has  all  escaped. 

Pure  sulphuric  ether  is  a  colorless  liquid,  of  a  hot,  pungent- 
taste,  and  fragrant  odor.  At  the  temperature  of  60°,  its  density 
is  0-72,  and  it  boils  at  96°  or  98°  in  the  atmosphere,  and  at  about 
40°  below  zero  in  a  vacuum.  In  the  open  air,  it  evaporates  with 
great  rapidity,  producing  intense  cold,  so  that  water  may  easily 
be  frozen  by  it  It  is  very  combustible,  and  burns  with  a  yellow 
flame.  Exposed  to  the  light,  in  vessels  partly  filled  with  air,  it 
gradually  absorbs  oxygen,  with  the  formation  of  acetic  acid. 
The  solvent  powers  of  ether  are  not  as  extensive  as  those  of 
alcohol,  but  it  dissolves  the  essential  oils,  resins,  and  many  of  the 
fatty  principles. 

606,  When  the  vapor  of  ether  is  inhaled,  it  first  produces  a 
species  of  intoxication,  similar  to  that  occasioned  by  exhilarating 

QUESTIONS. — 605.  Describe  the  mode  of  preparing  ether.  What  are 
its  properties  ?  606.  What  is  the  effect  when  vapor  of  ether  is  inhaled  f 


ETHERS.  435 

gas ;  and  afterwards  a  kind  of  stupor  follows,  during  which  the 
person  is  nearly  insensible  to  pain ;  the  effect  being  much  the 
same  as  that  produced  by  chloroform.  When  used  for  this  pur- 
pose, it  has  been  called  letheon. 

607.  Sulphovinic  Acid. —  Theory  of  the  Formation  of  Ether. — 
By  comparing  the  formula  of  alcohol,  C4H602  =  C4H50,HO,  with 
that  of  ether,  C4H50,  it  is  evident  that  the  former  may  be  con- 
sidered as  a  hydrate  of  the  latter  j  and  the  effect  of  the  acid  upon 
the  alcohol  in  producing  ether  is  simply  to  abstract  from  it  one 
equivalent  of  water,  or  its  elements.     But  although  this  is  the 
final  result,  other  intermediate  chemical  changes  take  place. 

When  equal  parts  of  sulphuric  acid  and  alcohol  are  mixed,  and 
slightly  heated,  sulphovinic  acid,  C4H50,2S03HO,  is  first  formed, 
and  may  be  obtained  in  a  free  state,  as  a  syrupy  liquid.  This 
acid  is  capable  of  combining  with  bases  and  forming  salts,  which  are 
called  sulphovinates,  as  sulphovinate  of  baryta,  BaO,C4H30,2SO3|, 
and  sulphovinate  of  lime,  CaO,C4H50,2S03.  These,  and  sulpho- 
vinates  of  other  bases,  are  easily  obtained  in  crystals. 

Sulphovinic  acid,  though  very  stable  at  ordinary  temperatures, 
is  decomposed  when  heated  to  about  310°,  and  ether  is  separated 
in  the  gaseous  state,  and  may  be  condensed,  the  sulphuric  acid 
and  water  remaining  behind.  Thus  we  have,  neglecting  the 
water  of  the  oil  of  vitriol, 

C4H602,2S03  =  C4H60  +  2S03,HO. 

608.  By  using  alcohol  nearly  pure,  and  regulating  the  temperature 
constantly  at  about  300°,  both  the  ether  and  the  water  formed  from  the 
alcohol  may  be  made  to  distil  over  together,  leaving  unchanged  the  acid, 
which  has  produced  the  whole  effect. 

Let  A  (see  figure  on  next  page)  be  a  flask,  with  rather  a  wide  mouth, 
'containing  a  mixture  of  five  parts  of  alcohol  and  eight  parts  of  sulphuric 
acid,  so  as  to  fill  it  about  half  full.  In  the  cork  insert  a  bent  tube,  B, 
through  which  the  alcohol  required  in  the  process  is  to  pass,  and  an- 
other, C,  to  connect  with  the  condenser  of  the  distilling  apparatus  (96)  ; 

QUESTIONS. — 607.  Why  may  alcohol  be  considered  a  hydrate  of  ether? 
What  is  the  effect ,  produced  upon  alcohol  by  sulphuric  acid  ?  What  is 
first  produced  when  equal  parts  of  alcohol  and  sulphuric  acid  are  mixed  ? 
What  is  the  composition  of  this  acid  ?  Is  it  capable  of  forming  salts  with 
bases  ?  What  is  the  effect  when  sulphovinic  acid  is  heated  ?  608.  De- 
Bcribe  the  mode  of  forming  ether  by  a  continuous  stream  of  alcohol. 


436 


ETHERS. 


o 

Preparation  of  Ether. 


and  between  them 
place  a  thermome- 
ter, T,  the  bulb  of 
•which  must  extend 
to  the  mixture  with- 
in, to  determine  the 
temperature.  So  also 
the  alcohol  tube,  B, 
should  extend  a  little 
below  the  surface  of 
the  liquid,  as  repre- 
sented in  the  figure. 
'When  the  mixture 
has  become  suffi- 
ciently heated,  a 
continuous  stream  of 
alcohol  is  made  to 
enter,  just  so  as  to 
keep  the  liquid  in 
the  flask  at  its  ori- 
ginal level.  The  sup- 
ply of  alcohol  is  regu- 
lated by  the  stopcock 
in  the  vessel  D,  which 
must  be  supported  a 
little  above  the  flask 
by  a  shelf  or  stand. 


The  ether  and  water  that  pass  over  are,  of  course,  collected  together; 
but,  as  they  do  not  mix,  the  ether  is  easily  separated.  The  mixture, 
during  the  operation,  should  be  kept  continually  boiling,  and  the  heat 
very  carefully  regulated. 

The  ether,  after  being  separated  from  the  water,  should  be  redistilled 
from  a  weak  solution  of  caustic  potash,  to  separate  it  from  any  acid 
which  may  have  passed  over  with  it. 

609.  Many  other  acids,  as  the  phosphoric,  arsenic,  carbonic, 
oxalic,  tartaric,  &c.,  produce  with  alcohol  vinic  acids — called  also 
coupled  acids  —  which  are  entirely  similar  to  the  sulphovinic. 
Such  acids  are  properly  to  be  considered  as  bibasic  (or  tribasic). 

To  indicate  the  basic  character  of  the  water  in  sulphovinic 
acid,  we  may  write  its  formulae,  HO,C4H60,2S03; —  now  this 
water  may  be  replaced  by  another  equivalent  of  ether,  C4H50, 
and  we  then  have  the  compound,  2(C4H50,S03),  which  is  per- 
fectly neutral,  and  is  called  a  compound  ether. 


QUESTIONS. — 609.  What  other  acids  are  mentioned  as  capable  of  form- 
ing vinic  or  coupled  acids  with  alcohol  ?     To  what  class  of  acids  do  they 


ETHERS.  487 

Some  acids,  as  the  sulphuric,  oxalic,  and  carbonic,  form  both 
vinic  acids  and  compound  ethers,  while  others,  as  the  phosphoric, 
form  only  vinic -acids;  and  others  still,  as  the  nitric  and  acetic, 
form  only  compound  ethers.  Acids  of  this  latter  kind  are  strictly 
monobasic. 

Besides  the  acids,  several  of  the  chlorides  (604),  as  the  chlorides 
of  zinc  and  tin,  and  the  fluoride  of  boron,  effect  the  transformation 
of  alcohol  into  ether,  with  the  elimination  always  of  an  atom  of 
water. 

By  distillation  with  an  alkaline  solution,  the  compound  ethers 
and  vinic  acids  are  decomposed,  and  alcohol  reproduced.  In  this 
case  the  acid  of  the  compound  ether,  or  vinic  acid,  combines  with 
the  alkali ;  and  the  ether,  C4H50,  as  it  is  set  free,  unites  with 
an  atom  of  water,  thus  reproducing  alcohol,  C4H602. 

610.  Hydrochloric  Ether,  C4H6C1. — This  ether  is  formed  by 
saturating  common  alcohol  with  hydrochloric  acid  gas,  and  then 
distilling  with  a  very  moderate  heat.  As  the  vapor  distils  over, 
it  should  be  made  to  pass  through  warm  water,  to  free  it  from 
impurities,  and  is  then  to  be  condensed  in  a  receiver  surrounded 
by  ice. 

It  may  also  be  formed  by  distilling  a  mixture  of  equal  parts 
of  alcohol  and  the  hydrochloric  acid  of  commerce,  and  by 
other  means. 

The  reaction  producing  it  is  shown  by  the  following  equation : 

C4H602  +  HC1  =  C4H5C1  +  2HO. 

This  ether  is  a  colorless  liquid,  which  has  a  density  of  0-874, 
and  boils  at  the  low  temperature  of  52°.  In  the  warm  weather 
of  summer,  it  can  be  preserved  only  in  tubes  hermetically  sealed. 

By  its  formula  it  will  be  seen  that  its  composition  ?s  the  same 

QUESTIONS. — What  acids  are  mentioned  as  forming  both  vinic  acids 
and  compound  ethers ?  What  as  forming  only  compound  ethers?  What 
is  their  character?  What  other  compounds  are  mentioned  as  being 
capable  of  transforming  alcohol  into  ether?  How  are  the  compound 
ethers  and  vinic  acids  affected  when  distilled  with  a  solution  of  alkali  ? 
610.  How  is  hydrochloric  ether  formed?  What  are  the  reactions  by 
which  it  is  produced  when  alcohol  and  hydrochloric  acid  are  used  ?  What 
are  some  of  the  properties  of  this  ether  ? 

37* 


438  ETHERS. 

as  that  of  sulphuric  ether,  except  that  the  oxygen  of  the  latter 
substance  is  replaced  by  chlorine. 

By  passing  a  current  of  chlorine  through  a  portion,  of  this  ether,  in 
direct  sunlight,  1  equivalent  after  another  of  the  *  hydrogen  is  replaced 
by  chlorine,  until  at  length  it  all  disappears,  and  we  have  only  the  com- 
pound C4C16.  We  have  therefore  the  following  series  of  compounds,  viz. : 

Boiling  Point.  Density. 

Hydrochloric  ether C4H5C1            52°      0-874 

Bichlorinated    do  C4H4C12           147°    1-174 

Trichlorinated  do   C4H3C13           167°    1-372 

Quadrichlorinated  ether    C4H2C14           215£° 1-539 

Quinquechlorinated  do  ..  C4HC16            295°    1-640 

Sesquichloride  of  carbon  C4H6  =  C2H3  356° 

Oil.  Hydrdbromie  Ether,  C4H5Br. — This  ether  is  prepared  from  a  mix- 
ture of  alcohol,  phosphorus,  and  bromine.  It  is  a  colorless  liquid,  having 
a  density  of  1-47,  and  boiling  at  106°. 

Hydriodic  Ether,  C4H5I. — Preparation  similar  to  the  preceding.  It  is 
a  limpid  liquid,  of  density  1-97,  and  boils  at  158°. 

Hydrosulphuric  Ether,  C4H5S. — This  ether  is  very  volatile,  colorless, 
and  of  a  penetrating,  nauseous  odor.  Its  density  is  0-825,  and  its  boiling 
point  163°. 

Hydrocyanic  Ether,  C4H5Cy. — A  poisonous,  volatile  liquid,  of  density 
•787,  and  having  its  boiling  point  at  180°. 

• 

II.    COMPOUND    ETHERS. 

612.  Sulphuric  Ether  (proper),  C4H50,S03.— This  is  the  only 
compound  properly  called  sulphuric  ether,  on  the  principles  adopted 
in  naming  the  other  compound  ethers. 

It  is  obtained  by  the  action  of  anhydrous  sulphuric  acid  upon 
ordinary,  ether.  It  is  a  neutral,  oily  liquid,  having  a  density  of 
1-12,  and  a  sharp,  burning  taste.  Heated  to  285°  or  300°,  it  is 
decomposed,  so  that  its  boiling  point  cannot  be  ascertained. 

613.  Hyponitrous  Ether,  C4H5N04  =  QgH50,N03.— This  ether 
may  be  formed  by  the  direct  action  of  nitric  acid  upon  alcohol ; 
but  a  better  mode  is  to  pass  a  current   of  nitrous  acid  vapor 
(obtained  by  the  action  of  nitric  acid  upon  starch)  through  dilute 

QUESTIONS. — What  is  the  effect  when  a  current  of  chlorine  is  passed 
through  hydrochloric  ether?  611.  What  other  simple  ethers  are  men- 
tioned ?  612.  What  is  the  composition  of  sulphuric  ether  proper  ?  How 
is  it  obtained  ?  613.  Describe  hyponitrous  ether. 


ETHERS.  4^ 

alcohol.  Heat  is  generated  by  the  process,  and  the  vapor  is 
condensed  in  a  cold  receiver.  As  the  action  of  the  acid  upon 
the  alcohol  is  often  very  tumultuous,  the  process  should  be  con- 
ducted with  caution.  Hyponitrous  ether  is  a  liquid  of  a  pale 
yellow  color,  and  fragrant  odor;  its  density  is  about  O94,  and  it 
boils  at  70°.  In  a  pure  state  it  cannot  be  kept  long ;  but  mixed 
with  alcohol  it  is  more  permanent,  and  is  extensively  used  in 
medicine,  under  the  name  of  sweet  spirits  of  nitre. 

Nitric  Ether,  04H5N06  =  C4H50,N05.— Nitric  ether  is  formed 
by  distilling  equal  parts  of  nitric  acid  and  alcohol  with  a  few  grains 
of  urea.  It  is  a  colorless  liquid,  of  a  sweet  taste,  and  is  heavier 
than  water.  It  boils  at  about  185°,  and  its  vapor  explodes 
by  heat.  * 

614.  Carbonic  Ether,  C4H50,C02. — This  ether  is  obtained  by 
distilling  oxalic  ether  (soon  to  be  described)  with  potassium  or 
sodium.      It  is  a  colorless  liquid,  very  volatile,  and  having  an 
aromatic  odor  and  acrid  taste.     Its  density  is  0-975,  and  it  boils 
at  259°.     With  chlorine  it  yields  several  chlorinated  carbonic 
ethers,  by   the  replacement  of  1   or  more   equivalents   of  the 
hydrogen  of  the  simple  ether,  C4H60,  by  an  equal  number  of 
equivalents  of  chlorine. 

615,  Silicic  Ethers. — Silicic  ethers,  of  which  there  are  two  (or 
perhaps  three),  are  formed  by  the  action  of  chloride  of  silicon 
upon  absolute  alcohol.     They  are  volatile  liquids,  having  a  pene- 
trating odor  and  a  pungent  taste.     By  water,  or  by  long  standing 
in  bottles,  from  which  the  air  is  not  perfectly  excluded,  they  are 
gradually  decomposed;   and  the  hydrated  silica  is  left^in  hard, 
vitreous  masses,  resembling  quartz. 

Acetic  Ether,  C8H804  =  C4H50,C4H303.  —  Acetic  ether  may 
be  prepared  by  several  modes,  but  the  best  is  to  distil  a  mixture 
of  3  parts  of  acetate  of  potash,  3  of  absolute  alcohol,  and  2  of 
sulphuric  acid.  Acetic  ether  is  a  volatile  liquid,  of  a  fragrant 
odor,  like  that  of  strong  vinegar.  It  boils  at  165°,  and  has  a 
density  of  about  0-89. 

QUESTIONS. — What  is  said  of  nitric  ether?  614.  Of  what  is  carbonic 
ether  composed?  615.  What  is  said  of  the  silicic  ethers?  What  of 
acetic  ether? 


440  ETHERS. 

616.  Oxalic  Ether,  C6H6O4  =  C4H50,C203.—This  ether  is  pre- 
pared by  distilling  a  mixture  of  4  parts  of  binoxalate  of  potash, 
5  parts  of  sulphuric  acid,  and  4  of  strong  alcohol,  and  thoroughly 
washing  the  product  with  water.     It  is  a  volatile  liquid,  which 
has  an  aromatic  odor,  and  is  a  little  heavier  than  water. 

Oxalic  ether  is  decomposed  by  contact  with  an  alcoholic  solution 
of  potash,  forming  alcohol  and  oxalic  acid.  Ammonia  acts  upon 
it,  producing  two  compounds,  called  oxamide,  C202NH3,  and 
oxamic  acid,  C405NH2,HO.  By  the  action  of  chlorine  upon 
it,  several  chlorinated  compounds  are  formed. 

617.  Formic  Ether,  C6H604  =  C4H50,C2H03.—  This  ether  is 
formed  by  distilling  a  mixture  of  dry  formiate  of  soda,  sulphuric 
acid,  and  strong  alcohol.     It  is  also  produced  in  considerable 
quantity  during  the  process  for  preparing  fulminating  mercury, 
to  be  hereafter  described. 

Formic  ether  is  a  colorless  liquid,  which  boils  at  about  130°, 
and  has  a  specific  gravity  of  0-915.  It  has  a  very  penetrating, 
agreeable  odor,  and  is  soluble  in  about  ten  times  its  weight  of 
water. 

Many  other  compound  ethers  of  the  wine  alcohol  series,  cannot  be  here 
described*  'Recent  writers  enumerate  nearly  a  hundred,  formed  by  the 
organic  acids  alone. 

In  their  composition  they  evidently  possess  the  character  of  salts, 
being  formed  by  the  union  of  ether,  C4H50,  acting  as  a  base,  with  the 
several  acids ;  but  in  their  properties  they  differ  essentially  from  proper 
saline  compounds.  This  appears  in  the  fact  that  the  acid  cannot  be 
detected  by  the  ordinary  tests;  thus,  oxalic  ether  is  a  compound  of 
vinic  ether,  C4H60,  and  oxalic  acid,  C203;  but  lime,  which  separates 
oxalic  acid  from  its  saline  compounds,  forming  oxalate  of  lime,  will  not 
separate  Jhis  acid  from  oxalic  ether. 

The  same  remark  applies  to  the  coupled,  or  vinic  acids. 

Ethers  of  Methylic  Alcohol. 

I.    SIMPLE    ETHEKS. 

618.  Methylic  Ether— Wood  Ether,  C2H30.— This  ether  is 
formed  from  methylic  alcohol,  in  the  same  manner  as  sulphuric 

QUESTIONS. — G16.  Plow  is  oxalic  ether  prepared  ?  617.  Formic  ether? 
How  are  the  compound  ethers  formed  ?  Are  they  really  salts  ?  Do  they 
differ  in  any  respect  from  proper  saline  compounds?  Illustrate  with 
reference  to  oxalic  ether.  618.  How  is  methylic  ether  formed  ? 


E  T  H  E  E  S  .  441 

ether  is  prepared  from  common  alcohol,  by  distilling  methylic 
alcohol  with  an  equal  volume  of  sulphuric  acid.  It  is  a  color- 
less gas,  of  a  pungent  odor  and  taste,  and  is  rapidly  absorbed  by 
cold  water,  but  given  off  again  unchanged  by  boiling.  It  is  con- 
densed to  the  liquid  form  by  a  temperature  of  — 3°;  and  is  chiefly 
interesting  as  taking  the  place,  in  this  series,  which  the  ether  first 
described  (605),  sometimes  called  sulphuric  ether,  occupies  in  the 
common  alcohol  series. 

The  theory  of  its  formation  corresponds  in  every  respect  with 
that  already  explained  (607)  in  describing  ordinary  or  sulphuric 
ether..  When  methylic  alcohol  and  sulphuric  acid  are  mixed, 
at  a  moderately  elevated  temperature,  sulplw-metliylic  acid  is 
formed,  having  the  composition,  C2H402,2S03  =  C2H3Q,2S03,HO, 
which,  by  further  elevation  of  temperature,  is  decomposed;  the 
methylic  ether  being  separated,  and  the  sulphuric  acid  and  water 
alone  remaining. 

619.  Hydrochloric  Methylic  Ether,  C2H3C1. — This  compound 
is  formed  by  distilling  a  mixture  of  common  salt,  wood-spirit,  and 
oil  of  vitriol.     It  is  a  colorless  gas,  of  a  peculiar  odor,  and  cor- 
responds to  the  ether  of  similar  name  in   the  common  alcohol 
series  ;  the  oxygen  of  the  preceding  compound  being  replaced  by 
chlorine. 

It  is  not  reduced  to  a  liquid  state  by  a  temperature  of  zero. 

By  the  action  of  chlorine  upon  this  ether,  in  the  direct  rays  of  the  sun, 
the  several  equivalents  of  hydrogen  may  be  successively  replaced  by 
chlorine,  as  heretofore  shown  in  another  case  (610),  and  important  com- 
pounds formed, — the  formulae  of  which,  with  their  densities  and  boiling 
points,  are  given  in  the  following  table : 

Boil.  Point.      Density. 

Hydrochloric  methylic  ether,  C2H3C1  ......    0-0°  1.74 

Bicblorinated         "  "       C3H2C12 87°  ......  1-34 

Trichlorinated       "  "       C2HC13  142°  1-49 

Sesquichloride  of  carbon,          CaII4      172°  1-60 

620.  Chloroform,  C2HC13,  is  the  trichlorinated  compound  of 
this  series.      It   is  produced  by  the  direct  action   of  chlorine 

QUESTIONS. — What  is  said  of  the  relation  methylic  ether  sustains  to 
methylic  alcohol  ?  What  is  sulpho-methylic  acid  ?  619.  Describe  hydro* 
chloric  methylic  ether.  What  is  the  eifect  when  a  current  of  chlorine  is 
made  to  pass  through  this  ether  ?  620.  What  is  chloroform  ? 


442  ETHERS. 

upon  hydrochloric  methylic  ether,  but  the  best  method  of  pre- 
paring it  is  "to  distil  a  mixture  of  hypochlorite  of  lime  (common 
bleaching  salt)  and  wine  alcohol,  or  wood-spirit. 

Chloroform  is  a  dense,  oily  liquid,  of  an  agreeable  ethereal  odor, 
and  sweetish  taste.  It  is  not  dissolved  by  water,  but  mixes  readily 
with  alcohol.  Its  density  is  149,  and  it  boils  at  about  142°.  By 
breathing  its  vapor  mixed  with  atmospheric  air,  a  kind  of  intoxica- 
tion is  produced,  much  like  that  occasioned  by  exhilarating  gas,  or 
the  vapor  of  sulphuric  ether.  If  the  vapor  is  breathed  some  time, 
total  insensibility  to  pain  is  produced,  and  loss  of  consciousness, 
during  which  difficult  surgical  operations  may  often  be  performed, 
without  even  the  knowledge  of  the  patient. 

It  readily  dissolves  caoutchouc  and  gutta  percha,  and  solid 
carbonic  acid. 

By  alcoholic  solution  of  potash,  chloroform  is  changed  into 
formiate  of  potash  and  chloride  of  potassium.  It  was  this  cir- 
cumstance that  suggested  the  name  chloroform. 

lodoform,  C2HI3,  bromoform,  C2HBr3,  and  sulphoform,  C2HS3,  are  analo- 
gous compounds  of  iodine,  bromine,  and  sulphur. 

621.  Hydriodic  Methylic  Ether,  C2H3I,  is  a  colorless  liquid,  obtained 
by  distilling  a  mixture  of  iodine,  methylic  alcohol,  and  phosphorus.     It 
is  remarkable  for  its  great  density,  which  is  2-24. 

Hydrobromic  Methylic  Ether,  C2H3Br,  is  prepared  in  a  manner  similar 
to  the  above,  only  substituting  bromine  instead  of  iodine.  It  is  liquid  at 
temperatures  below  55°. 

Hydrosulphuric  Methylic  Ether,  C2H3S,  is  a  liquid,  of  a  density  0-845, 
which  boils  at  106°. 

Still  other  simple  methylic  ethers  are  known,  but  they  cannot  be  here 
described. 

II.    COMPOUND    METHYLIC     ETHERS. 

622.  Sulphuric  Methylic  Ether,  C2H30,S03.  —  This  ether  13 
formed  by  distilling  1  part  of  methylic  alcohol  with  8  or  10  parts 
of  sulphuric  acid.     It  is  a  liquid,  having  a  density  of  1-32,  and 
boils  at  370°. 

Nitric  Methylic  Ether,  C2H3N06  =  C2H30,N05.~ This  ether 
corresponds  to  the  ether  of  similar  name  in  the  common  alcohol 

QUESTIONS. — How  is  chloroform  prepared?  What  use  is  made  of  it? 
621.  What  other  methylic  ethers  are  mentioned?  622.  How  is  sul- 
phuric methylic  ether  formed  ?  Describe  nitric  methylic  ether  ? 


ETHERS.  448 

series.  It  is  formed  by  distilling  a  mixture  of  wood-spirit,  nitrate 
of  potash,  and  sulphuric  acid.  It  is  a  dense,  colorless  liquid, 
which  boils  at  about  150°.  Its  vapor,  when  heated  to  248°,  is 
decomposed  with  a  violent  explosion. 

Oxalic  Methylic  Ether,  C4H304  =  C2H3OC203.  —  Oxalic  me- 
thylic  ether  is  prepared  by  distilling  a  mixture,  in  proper  pro- 
portions, of  sulphuric  acid,  binoxalate  of  potassa,  and  methylic 
jalcohol.  At  ordinary  temperatures,  it  is  a  white  crystaline  solid, 
which  melts  at  124°,  and  boils  at  322°. 

Acetic  Methylic  Ether,  C6H604  =  C2H30,C4H303.— This  ether 
is  formed  by  distilling  an  acetate  with  methylic  alcohol,  and  sul- 
phuric acid.  It  is  always  formed  in  the  distillation  of  wood.  It 
is  a  colorless  liquid,  of  an  agreeable  ethereal  odor,  and  has  a  specific 
gravity  of  0-919.  It  boils  at  a  temperature  of  137°. 

The  close  resemblance  between  the  methylic  ethers  and  those  of  the 
common  alcohol  group  will  be  seen  at  once.  There  are  many  more 
of  this  group,  which  cannot  be  here  described,  late  writers  enumerating 
more  than  seventy. 

Ethers  of  Amylic  Alcohol. 

623.  Amylic  alcohol,  treated  with  sulphuric  acid,  produces 
sulphoamylic  acid,  similar  to  the  sulphovinic  and  sulphomethylic 
acids,  which  is  easily  obtained  in  combination  with  bases,  but 
with  difficulty  in  a  free  state. 

Treated  with  an  excess  of  concentrated  sulphuric  acid,  and 
heated  to  boiling,  a  carburetted  hydrogen,  C10H,0,  is  obtained, 
called  amylene,  which  is  a  volatile,  colorless  liquid,  boiling  at 
102°.  At  the  same  time  two  other  compounds,  isomeric  with 
it,  are  usually  obtained,  called  paramylene,  $%$.<&  and  metamy- 
lene,  C^H^, 

624.  Amylic  Ether,  C,0HU0. — This  ether  is  prepared  from 
the  hydrochloric  amylic  ether,  to  be  next  described,  by  the  action 
of  a 'strong  solution  of  potassa.     It  is  a  liquid  of  an  agreeable 
odor,  the  boiling  point  of  which  is  about  234°. 

QUESTIONS. — What  is  said  of  the  resemblance  between  the  methylio 
'  ethers  and  those  of  the  common  alcohol  series  ?     623.  What  is  said  of  the 
sulphoamylic  acid  ?     What  is  amylene  ?     What  two  substances  isomeric 
with  it  are  mentioned  ?     624.  What  is  amylic  ether  ? 


444       ,  VOLATILE    OILS. 

This  ether,  it  will  be  seen,  corresponds  precisely  to  common 
ether  in  the  wine  alcohol  group  of  ethers,  and  to  methylic  ether 
in  the  methylic  alcohol  group. 

Hydrochloric  Amylic  Ether,  C,oHnCl. — To  obtain  this  ether, 
equal  parts  of  amylic  alcohol  and  perchloride  of  phosphorus  are 
distilled  in  a  glass  retort,  and  the  vapor  condensed  in  the  ordinary 
mode.  It  is  a  colorless  liquid,  with  an  aromatic  odor,  and  boils 
at  about  215°. 

If  may  also  be  obtained  b;y  the  action,  long  continued,  of  hydro- 
chloric acid  upon  alcohol. 

625.  Ilydriodic  amylic  ether,  C10H,,I,  and  hydrosulphuric  amylic  ether, 
C10HnS,  are  known.  The  latter  has  the  smell  of  onions. 

Acetic  Amylic  Ether,  C14H1404==C,0H,,0,C4H3p3.— To  prepare  acetic 
amylic  ether,  equal  parts  of  amylic  alcohol  and  oil  of  vitriol  are  distilled 
with  2  parts  of  acetate  of  potash,  and  the  resulting  liquid  purified.  It  is 
a  limpid  liquid,  a  little  lighter  than  water,  with  an  agreeable  aromatic 
odor.  Its  boiling  point  is  257°.  By  some  its  composition  is  said  to  be 
3(C10HU0),C4H303. 

The  odor  of  this  ether  closely  resembles  that  of  the  ripe  banana  fruit, 
and  it  is  used  to  give  the  banana  flavor  to  sugar-candy.  The  preparation 
is  sometimes  called  banana  drops.  The  peculiar  flavor  of  many  ripe 
fruits  may  in  this  mode  be  very  closely  imitated  by  the  use  of  ethers. 

Oxalic  Amylic  Ether,  C,2Hn03=C10HuO,C203. — This  compound  is  pro- 
cured by  distilling  a  mixture  of  amylic  alcohol  and  oxalic  acid.  It  is 
liquid  at  ordinary  temperatures,  and  boils  at  500°.  Its  odor  is  exceed- 
ingly offensive. 

VOLATILE,    OR    ESSENTIAL    OILS. 

626.  These  oils  constitute  a  very  numerous  class  of  compounds, 
and,  as  the  name  indicates,  are  distinguished  by  being  volatile  at 
ordinary  or  slightly  elevated  temperatures.  Most  of  them  are 
liquid  at  a  temperature  of  50°,  or  above ;  but  a  few  are  solid,  as 
common  camphor. 

They  are  also  usually  distinguished  by  their  powerful  odor, 
which  is  often  very  agreeable.  Most  of  them  are  obtained  from 

QUESTIONS.- — What  relation  does  amylic  ether  sustain  to  this  series 
of  ethers?  What  other  ethers  of  .this  series  are  mentioned?  625.  What 
is  said  of  the  odor  of  acetic  amylic  ether  ?  626.  What  is  said  of  the 
volatile  oils  ?  Are  any  of  them  solid  at  ordinary  temperatures  ?  What 
ia  said  of  their  odor  ?  From  what  are  they  obtained  ? 


VOLATILE    OILS.  445 

the  leaves  and  stalks  of  plants,  but  some  are  found  in  the  flowers, 
fruit,  bark,  wood,  or  in  the  pericarp. 

In  general,  these  oils  are  obtained  by  distilling  the  part  of  the 
plant  containing  them,  with  water; — both  the  oil  and  the  water 
pass  over  in  vapor,  and  are  condensed  in  the  usual  mode ;  and  are 
afterwards  separated  by  the  oil  rising  to  the  surface.  In  a  few 
cases  only  is  the  oil  heavier  than  water,  when, 
as  a  matter  of  course,  it  sinks  to  the  bottom. 

To  separate  such  as  are  lighter  than  water,  a 
vessel  of  the  form  represented  in  the  margin  answers 
well.  It  is  simply  a  vessel  of  proper  size,  with  a 
small  spout  which  starts  nearly  from  the  bottom, 
and  rises  nearly  as  high  as  the  mouth.  It  is  first 
filled  with  water  to  the  line  A,  and  then  the  mixed 
liquids  are  poured  into  it  in  a  small  stream,  the  oil 
remaining  at  the  surface,  while  the  water  escapes 
at  C.  This,  it  is  evident,  may  be  continued  until 
the  vessel  is.  nearly  filled  with  the  pure  oil ;  or  until, 
if  more  were  added,  the  oil  itself  would  begin  to 
escape  by  the  spout  C.  Separating  Volatile  Oils. 

Water  is  necessary  in  the  distilling  process,  to  prevent  the  decom- 
position of  a  portion  of  the  oil  by  the  heat ;  and  in  most  cases  the 
distillation  can  be  effected  in  this  mode,  even  though  the  boiling 
point  of  the  oil  be  considerably  above  that  of  water.  In  some 
cases,  a  higher  temperature  than  212°  is  required,  when  some 
soluble  salt  is  added  to  the  water,  as  common  salt;  a  saturated 
solution  of  this  compound  boiling  at  about  230°. 

Some  few  of  the  essential  oils  are  obtained  from  the  plant 
by  pressure,  or  by  the  action  of  a  solvent,  as  alcohol  or  ether. 

627.  These  oils  being  volatile,  if  a  small  portion  is  dropped  on 
a  piece  of  white  paper,  the  stain  produced  soon  disappears,  espe- 
cially if  -the  paper  be  warmed.  In  this  way  they  may  be  dis- 
tinguished from  other  oils,  which  produce  upon  paper  a  permanent 
stain. 

Most  of  the  essential  oils  consist  of  at  least  two  principles ;  one 
of  which  is  less  fusible  than  the  other,  and  may  be  separated  by 
cold.  Thus,  exposing  oil  of  peppermint  to  severe  cold,  a  solid 

QUESTIONS. — Why  is  water  necessary  in  distilling  these  oils  ?     627.  How 
may  the  volatile  oils  be  distinguished?     What  is  said  of  the  composition 
of  most  of  them  ? 
88 


446  VOLATILE    OILS. 

not  unlike  camphor  is  crystalized  out,  and  may  be  separated  from 
the  portion  that  remains  liquid.  These  solids,  sometimes  called 
stearoptens,  are  different  in  the  different  oils;  some  being  much 
more  easily  solidified  than  others.  Their  composition  is  also 
various ;  some  being  isomeric  with,  the  oil  which  yields  them,  and 
others,  hydrates  or  oxides  of  the  oil. 

Most  of  them  exist,  as  such,  in  the  plant  or  part  of  the  plant 
from  which  they  are  obtained,  but  some  are  formed  in  the  process 
of  distillation  from  materials  contained  in  the  substance  distilled. 

628.  If  we  have  regard  to  the  elements  of  which  these  oils  are  com- 
posed, we  may  divide  them  into  three  classes,  viz. : 

1.  Oils  composed  entirely  of  carbon  and  hydrogen. 

2.  Oils  which,  in  addition  to  the  above  elements,  also  contain  oxygen ;  and 

3.  Oils  of  which  sulphur  is  an  ingredient ; — these  also  usually  contain 
nitrogen. 

Carbo-liydrogen  Volatile  Oils. 

629.  Oil  of  Turpentine— Camphene,  C20H16. — This  oil  is  pro- 
cured by  distilling  common  turpentine  with  water.  Turpentine 
is  obtained  from  several  species  of  the  pine,  in  the  wood  of  which 
it  is  contained  in  large  quantities.  At  the  proper  seasons  of  the 
year,  incisions  are  made  with  an  axe  in  the  trunks  of  the  trees, 
from  which  it  gradually  exudes,  and  is  collected  and  preserved. 
This  viscous  substance  is  a  solution  of  resin  (common  rosin")  in 
oil  of  turpentine,  and  the  latter  is  separated  in  the  process  of 
distillation. 

Common  spirits  of  turpentine  is  an  impure  camphene,  con- 
taining a  portion  of  resin  in  solution. 

Exposed  to  the  air,  oil  of  turpentine  evaporates  rapidly,  but  at 
the  same  time  oxygen  is  absorbed,  and  a  portion  of  the  oil  is  con- 
verted into  resin,  which  remains  in  solution.  It  can  therefore  be 
preserved  pure  only  in  vessels  from  which  the  air  is  perfectly 
excluded.  When  pure,  it  is  a  limpid  liquid,  of  specific  gravity 
0-87,  which  boils  at  315°. 

QUESTIONS. — Do  the  essential  oils  exist  ready  formed  in.  the  plant? 
628.  Into  what  three  classes  may  they  be  divided?  629.  How  is  oil 
of  turpentine  procured  ?  From  what  is  it  obtained  ?  What  are  the 
ordinary  spirits  of  turpentine  ? 


VOLATILE    OILS.  447 

Oil  of  turpentine  is  not  soluble  in  water,  but  dissolves  readily 
in  alcohol  and  ether,  and  in  other  essential  oils.  Mixed  with 
three  or  four  times  its  volume  of  strong  alcohol,  it  constitutes  the 
ordinary  burning  fluid. 

When  left  for  some  time  in  contact  with  water,  a  portion  of  the  two 
unite,  forming  a  solid  hydrate  of  camphene,  which  has  the  formula, 
C201I16,6HO.  Other  hydrates  may  also  be  prepared,  containing,  seve- 
rally, 4,  2,  and  1  equivalents  of  water. 

Many  substances,  as  caoutchouc,  insoluble  in  alcohol  and  ether,  dis- 
solve readily  in  this  oil,  which  renders  it  an  important  substance  in  the 
arts.  It  is  also  largely  used  in  mixing  paints,  in  the  manufacture 
of  varnishes,  and  in  the  practice  of  medicine. 

630.  Hydro  chlorate  of  camphene,   or  artificial  camphor,  C20H]6,HC1,  is 
prepared  by  passing  a  current  of  dry  hydrochloric  acid  gas  through  pure 
oil  of  turpentine.     It  makes  its  appearance  as  a  white  crystaline  solid, 
which  melts  at  about  302°,  and  may  be  sublimed,  without  change,  at 
about  338°.      In  many  of  its  ^properties  it  closely  resembles  common 
camphor. 

The  portion  which  remains  liquid  has  the  same  composition  as  the 
crystals,  but  it  cannot  be  solidified,  so  far  as  is  known,  by  any  tem- 
perature. 

Hydriodic  and  hydrobromic  acids  form  with  oil  of  turpentine  com- 
pounds similar  to  those  formed  by  the  hydrochloric. 

Sulphuric  and  nitric  acids  act  readily  upon  oil  of  turpentine,  forming 
several  interesting  compounds. 

631.  Oil  of  Lemons,  CIOH8. — This  oil  is  obtained  by  pressure 
from  the  yellow  part  of  the  peel  of  the  fruit,  and  is  isomeric  with 
the  preceding,  having  the  same  ultimate  composition,  but  its  equiva- 
lent being  only  one-half  that  of  oil  of  turpentine.    By  distillation  it 
yields  two  oils,  which  differ  in  their  boiling  points. 

Oil  of  lemons  has  a  specific  gravity  of  0-847,  and  it  boils 
at  338°. 

By  the  action  of  hydrochloric  acid,  it  forms  two  camphors, 
similar  to  those  formed  from  oil  of  turpentine,  one  being  solid 
and  the  other  liquid. 

Orange  peel  yields  an  oil  isomeric  with  the  above,  but  having  a  dif- 
ferent specific  gravity,  and  a  different  boiling  point. 

Oil  of  elemi,  oil  of  juniper,  oil  of  pepper,  &c.,  have  a  similar  composition 
to  the  above,  and  they  are  all  isomeric. 

QUESTIONS.  — What  is  the  effect  when  oil  of  turpentine  is  left  in  contact 
with  water?  What  use  is  made  of  this  oil?  630.  What  is  artificial  cam- 
phor? How  is  it  formed?  631.  Describe  the  oil  of  lemons.  What  is 
baid  of  oil  of  elemi,  oil  of  juniper,  £c.  ? 


448  VOLATILE    OILS. 


Oxygenated  Volatile  Oils. 

632.  Oil  of  Bitter  Almonds.—  Benzoic  Series  of  Compounds, 

•  —  Bitter  almond  oil,  C,4H602,  is  obtained  from  the  kernels  of 
bitter  almonds  by  distillation  with  water  after  the  fixed  oil  con- 
tained in  the  seed  has  been  expressed.  It  does  not  pre-exist  in 
the  seed,  but  is  formed  from  the  amygdaline  of  the  seed,  in  a 
manner  soon  to  be  explained.  Its  density  is  a  little  above  that 
of  water,  and  it  boils  at  356°.  It  is  quite  colorless,  and  has  a 
pungent  taste  and  fragrant  odor,  and  is  poisonous. 

After  the  fixed  oil  has  been  expressed,  the  pulp  is  allowed  to 
stand  for  some  hours,  and  a  kind  of  fermentation  takes  place  in 
the  amygdalkie  by  virtue  of  the  presence  of  another  proximate 
principle  contained  in  the  almond,  called  synaptase,  or  emulsine. 
During  this  fermentation  there  are  produced,  besides  the  oil, 
hydrocyanic  acid  and  glucose. 

633.  Amygdaline,  C40H27N022,  may  be  obtained  in  a  free  state.     It  is  a 
crystaline,  colorless  powder,  very  soluble  in  water  and  alcohol.     Synaptase 
also  may  be  isolated  ;  —  it  is  a  yellowish-white  solid. 

634.  Chlorinated  Oil  of  Bitter  Almonds—  Chloride  of  Benzyle,  C14TT6C102. 
—  This  substance  is  obtained  by  passing  a  current  of  dry  chlorine  through 
oil  of  bitter  almonds,  and  expelling  the  excess  of  chlorine  by  heat.     It  is 
a  colorless  liquid,  heavier  than  water,  and  has  a  peculiar,  disagreeable 
odor.     It  is  formed  from  the  oil  by  the  substitution  of  an  atom  of  chlorine 
for  one  of  hydrogon.     Iodine  and  bromine  form  similar  compounds. 

When  this  chlorinated  oil  is  treated  with  gaseous  ammonia,  there  are 
formed  benzamide,  C14H602,NH2,  and  hydrochlorate  of  ammonia.  Thus, 


C14H5C102  +  2NH3  =  C14H602,NKJ  +  NH3,HC1 

Benzamide  is  a  white  crystaline  solid,  and  may  be  entirely  purified 
from  the  sal-ammoniac  by  washing  it  with  water.  By  remaining  long 
in  contact  with  water,  benzamide  is  converted  into  hydrobenzamide, 
C^HjgNg.GHO;  and  this,  by  solution  in  alcohol  and  boiling,  is  recon- 
verted into  bitter  almond  oil  and  ammonia. 

Benzoic  Acid.  —  When  exposed  to  the  atmosphere,  oil  of  bitter 
lilrnonds  rapidly  absorbs  oxygen,  and  is  converted  into  lenzoic 
acid,  C14H604  =  CUH603,HO.  This  acid  is  also  formed  when 

QUESTIONS.  —  G32.  Describe  bitter  almond  oil.  From  what  proximate 
principle  contained  in  the  kernel  is  the  oil  formed?  G33.  Describe 
amygdaline.  634.  Describe  the  chlorinated  oil.  Describe  benzoic  acid. 


VOLATILE    OILS.  449 

the  oil  is 'boiled  with  a  solution  of  potassa.  It  is  a  beautiful, 
crystaline  solid,  which  melts  at  248°,  and  boils  at  about  463°. 
It  may,  however,  be  sublimed  at  a  temperature  considerably 
below  its  boiling  point. 

Benzoic  acid  is  found  in  considerable  quantity  in  the  resinous 
substance  usually  called  gum  benzoin,  a  product  of  the  laurus 
benzoin.  From  this  compound  it  may  be  procured  by 
direct  sublimation,  in  the  following  manner.  Place  a 
small  quantity  of  the  resin,  coarsely  powdered,  upon  a 
plate  of  metal  on  a  stand,  and  put  over  it  a  glass  receiver, 
having  suspended  in  it  a  small  twig  of  mint,  or  other 
substance,  as  shown  in  the  figure,  and  apply  the  heat  of 
a  lamp  beneath  it.  In  a  short  time  the  leaves  will  be 
covered  with  delicate  crystals  of  the  acid.  * 

Benzoic  acid  with  bases  forms  numerous  salts  called  ben- 
zoates,  but  none  of  them  are  of  sufficient  importance  to  require 
description  here. 

635.  Benzoic  Ether,  C4H50,CI4H503,  is  formed  by  distilling  a 
mixture  of  1  part  of  benzoic  acid,  2  parts  of  alcohol,  and  6  parts 
of  hydrochloric  acid.     It  is  a  colorless  liquid,  heavier  than  water, 
and  boiling  at' 410°.     By  substituting  methylic  instead  of  wine 
alcohol  in  the  mixture,  benzoic-methylic  ether  is  formed,  which 
boils  at  226°. 

636.  Benzoine,  C28H1204,  is  formed  when  crude  oil  of  bitter  almonds  is 
shaken  with  an  alcoholic  solution  of  potassa,  and  is  separated  by  crys- 
talization.      The  crystals  melt  at  248°.      It  is   isomeric  with   the  oil. 
It  may  be  sublimed  without  change ;  but  by  passing  its  vapor  through  a 
red-hot  tube  the  oil  is  reproduced. 

By  heating  benzoine  with  nitric  acid,  it  loses  2  equivalents  of  its 
hydrogen,  and  a  new  compound  is  formed,  called  benzile.  By  the  ad- 
dition of  oxygen,  benzilic  acid  is  formed. 

637.  Benzone,  CnH1008,  is  a  compound  formed  when  benzoate  of  lime 
is  distilled.     It  is  a  solid,  little  soluble  in  water,  but  very  soluble  in  alco- 
hol and  ether. 

638.  Benzene,  C,2H6,  at  ordinary  temperatures,  is  a  liquid  of  specific 
gravity  0-85,  which  boils  at  187°.  •    It  ia  formed  by  distilling  a  mixture 
of  3  parts  of  dry  recently-slaked  lime  and  1  part  of  benzoic  acid.     It  ia 

QUESTIONS. — Describe  the  mode  of  subliming  a  small  quantity  of  benzoio 
acid.  635.  Describe  benzoic  ether.  636.  Describe  benzoine.  637.  Ben- 
zone.  638.  Benzene. 

98* 


450  VOLATILE    OILS. 

of  a  sweet  taste  and  agreeable  odor,  and  crystalizes  when  cooled  to  32°. 
It  has  also  been  called  benzol  and  phene ;  and  is  produced  by  the  decom- 
position of  many  organic  substances  by  heat. 

639.  Oil  of  Spiraea  TJlmaria,— Salicine  Series  of  Compounds. 

— Flowers  of  the  plant  called  meadow-sweet  (spiraea  ulmaria), 
when  distilled  with  water,  yield  an  acid  essential  oil,  CUH604, 
which,  like  the  oil  of  bitter  almonds,  is  of  special  interest  because 
of  its  intimate  relations  with  numerous  other  compounds.  It  doea 
not  pre-exist  in  the  flowers,  but  is  formed  in  the  process  of  dis- 
tillation. It  is  a  liquid  more  dense  than  water,  and  boils  at  385°. 
In  composition  it  is  isomeric  with  benzoic  acid,  and  is  sometimes 
called  salicylous  acid. 

640.  Salicjne,  C26'H18014,  is  a  substance  obtained  from  the  bark 
of  certain  species  of  willow  (salix),  and  from  many  other  plants, 
by  digesting  them  with  water,  and  then  precipitating  the  gummy 
matter  also  contained  in  the  solution  by  boiling  with  oxide  of 
lead.     After  precipitating  the  lead  by  means  of  sulphuric  acid, 
and  sulphide  of  barium,  salicine  is  obtained  by  evaporation  in 
small,  white,  acicular  crystals.     Its  taste  is  bitter,  and  it  is  very 
soluble  in  hot  water  and  alcohol,  but  not  in  ether.     Cold  sul- 
phuric acid  dissolves  it,  forming  a  deep  red  solution. 

A  mixture  of  equal  parts  of  salicine  and  bichromate  of  potash, 
digested  for  some  time  with  6  or  8  times  their  combined  weight 
of  dilute  sulphuric  acid,  and  afterwards  distilled,  yields  salicylous 
acid,  or  oil  of  spiraea  ulmaria,  described  above. 

Treated  with  dilute  sulphuric  or  hydrochloric  acids,  or  with  nitric 
acid,  various  other  compounds  are  produced,  which  cannot  be  here 
described. 

641.  Salicylic  Acid,  C,4H606  =  C14H505,HO.— This  acid  is  formed  when 
salicylous  acid  is  heated  with  an  excess  of  caustic  potash.  The  alkali  is 
then  separated  by  a  mineral  acid,  and  the  salicylic  acid  is  obtained  in 
colorless  crystals,  which  are  soluble  in  boiling  water  and  in  alcohol  and 
ether. 

"When  salicylic  acid  is  distilled  with  an  excess  of  lime,  carbonic  acid 
and  a  new  compound  called  phenol  or  phenylic  alcohol,  C12H602,  are 
formed.  Thus, 

=  C12H602-f2C02. 


QUESTIONS. — 639^  Describe  the  mode  of  procuring  oil  of  spiraea  ulmaria. 
640.  Describe  salicine.  How  is  salicylous  acid,  or  the  oil  last  mentioned, 
obtained  from  salicine  ?  641 .  Describe  salicylic  acid.  What  is  phenol 
or  phenylic  alcohol  ? 


VOLATILE    OILS.  451 

Phenol  is  sometimes  classed  with  the  acids,  and  called  carbolic  acid. 
It  resembles  the  alcohols  in  many  of  its  properties. 

642.  By  distilling  a  mixture  of  2  parts  of  absolute  alcohol,  1  part 
of  sulphuric,  and  1  \  parts  of  salicylic  acid,  salicylic  ether,  C4H60,C14H606> 
is  obtained.     It  is  a  dense  liquid,  boiling  at  437°,  and  possesses  acid 
properties,  readily  combining  with  bases  and  forming  proper  salts.     By 
substituting  methylic  alcohol  in  the  above  mixture,  and  using  2  parts 
of  salicylic  acid,  we  obtain  salicylic  methylic  ether,  C2H30,Ci4H505,  which 
is  of  special  interest  as  being  identical  with  the  chief  constituent  of  oil 
of  winter- green  (gaultheria  procumbens),  a  substance  well  known,  as  obtained 
by  distilling  with  water  the  leaves  and  berries  of  this  plant. 

The  oil  is  an  aromatic  liquid,  heavier  than  water,  having  its  boiling 
point  at  435°. 

643.  Oil  of  Cinnamon.  —  Cinnamic  Series  of  Compounds.— 
Oil  of  cinnamon  is  prepared   by  distilling  with. water  the  cin- 
namon of  commerce,  which  is  the  prepared  bark  of  two  or  more 
species  of  trees,  found  in  Ceylon  and  other  Eastern  countries. 
It  possesses  the  peculiar  taste  and  odor  of  the  bark.     Its  compo- 
sition when  pure  seems  to  be  C,8H802,  but  when  exposed  to  the 
air  it  absorbs  oxygen,  and  perhaps  undergoes  other  changes  not 
understood,  so  that  different  chemists  have  arrived  at  different 
results  as  regards  its  true  composition. 

644.  Cinnamic  Acid,  C18H703,HO,  is  always  found  in  the  oil 
after  it  has  been  kept  for  a  time  exposed  to  the  air,  and  is  also 
contained  with  benzoic  acid  in  the  balsams  of  Tolu  and  Peru. 
It   is   a   crystaline   solid,   which   melts   at   264°,  and   boils   at 
about  570°. 

Cinnamic  acid  forms  ethers  with  common  and  methylic  alco- 
hols, analogous  to  those  formed  by  salicylic  acid. 

When  vapor  of  cinnamic  acid  is  made  to  pass  through  a  glass  tube 
heated  to  dull  redness,  it  is  decomposed,  and  a  carbo-hydrogen,  C16H8,  is 
formed,  called  cinnamene.  It  is  a  colorless  liquid,  of  an  agreeable,  pene- 
trating odor.  This  compound  may  also  be  obtained  from  the  resinous 
substance  called  styrax,  and  has  in  consequence  sometimes  received  the 
name  styrole. 

By  treament  with  different  reagents,  still  other  compounds  belonging 
to  this  series  may  be  obtained. 

645.  Oil  of  Aniseed.— Anisic  Series  of  Compounds.— Aniseed 
(the  seeds  of  the  anisem  sativum'),  when  distilled  with  water, 

QUESTIONS. — 642.  Describe  salicylic  ether.  What  is  said  of  the  oil 
of  winter-green?  643.  How  is  oil  of  cinnamon  procured?  644.  'De- 
scribe cinnamic  acid.  645.  Describe  aniseed  oil. 


452  VOLATILE    OILS. 

yields  an  essential  oil  from  which  crystals  are  deposited  at  a  low 
temperature,  having  the  composition,  C2oH1202.  Treated  with 
reagents,  it  forms  a  series  of  compounds  known  as  the  anisic 
series.  Among  them  are  anisic  acid,  C,6H705,HO,  which,  with 
wine  and  methylic  alcohols,  yields  ethers,  and  anisene,  C,4HS. 
These  sustain  the  same  relation  to  each  other,  and  to  the  oil,  as 
cinnamon  sustains  to  cinnamic  acid  and  the  oil  of  cinnamon. 

646.  Oil  of  Cumin,  obtained    by  distilling   with   water  the 
seeds  of  the   cuminum  cyminum,  treated  in   a  similar  manner 
with  reagents,  forms  a  series   of  compounds,  analogous  to   the 
above.     Another  series;  called  the  eugenic  series,  is  formed  from 
the  oil  of  cloves  or  oil  of  pimento. 

647.  Oil  of  Peppermint,  C20H2002,  is  contained  in  the  leaves 
and  stem  of  the  plant,  from  which  it  is  separated  by  distillation 
with  water.     This  oil  is  used  in  large  quantities  by  confectioners ; 
and  in  some  of  the  western  states,  the  plant  is  extensively  cul- 
tivated, to  be  distilled  for  the  oil.  •  Dissolved  in  alcohol,  it  forms 
the  well-known    essence   of  peppermint.      This   is  the  general 
method  of  preparing  what  are  called  essences. 

Oil  of  peppermint  is  liquid  at  ordinary  temperatures;  but, 
when  cooled  gradually,  it  deposites  a  white  crystaline  stearopten 
(627),  resembling  camphor,  which  has  the  same  composition  as 
the  oil. 

There  are  very  many  other  oxygenated  volatile  oils,  but  as  they 
possess  no  properties  giving  them  peculiar  interest,  they  cannot  be 
here  described. 

Sulphuretted  Volatile  Oils. 

648.  OH  of  Black  Mustard,  C8E5NS2.— This  oil  does  not  exist,  as  such, 
in  the  seed,  but  is  formed  from  substances  contained  in  them,  after  the 
fixed  oil  has  been  expressed,  as  in  the  case  of  bitter  almond  oil.     The 
active   substances   in   the    mustard-seed,    producing   the    oil   when   the 
bruised  seed  is  digested  -with  water,  are  called  myrosine  and  myronic  acid, 
both  of  which  have  been  isolated ;   but  their  composition  has  not  been 
determined. 

Oil  of  mustard  is  a  colorless  liquid,  boiling  at  293°,  and  forming  a  most 
pungent,  irritating  vapor.  Treated  with  reagents,  it  forms  several  other 
compounds. 

QUESTIONS. — 646.  From  what  is  oil  of  cumin  obtained?  647.  De- 
scribe oil  of  peppermint.  648.  What  is  the  composition  of  oil  of  black 
mustard  ? 


VOLATILE    OILS. 


453 


649.  Oil  of  Garlic,  C6H5S. — This  oil  is  procured  by  distilling  garlic  with 
water,'  and  redistilling  the  product  first  obtained  in  a  salt-water  bath, 
and  then  rectifying  it  with  potassium.     It  is  a  colorless  liquid,  lighter 
thiiii  water,  and  of  an  offensive  odor.     It  has  been  called  sulphide  of  alyl, 
being  composed  of  sulphur  and  the  carbo-hydrogen,  C6H6,  called  alyl. 

Camphors. 

650.  The  camphors  are  allied  both  to  the  essential  oils  and  to 
the  resins.     There  is  a  large  number  of  them,  if  we  include  the 
stearoptens  (627),  deposited  at  low  temperatures  from  the  vola 
tile  oils;   but  only  common   or  Japan    camphor,   and   Borneo 
camphor,  with  a  few  of  the  compounds  formed  from  them,  will 
be  here  described 

651.  Common,  or  Japan  Camphor,  C20H1602. — This  substance, 
which  is  always  seen  as  a  white  crystaline  solid,  is  obtained  by 
distilling  with  water  the  roots 

and  wood  of  the  laurus  cam- 
phor a,  a  tree  found  in  the 
island  of  Japan,  and  other  parts 
of  the  East  (see  figure).  It  is 
a  little  lighteAhan  water,  and 
is  readily  soluble  in  alcohol, 
and  ether,  and  every  variety  of 
ardent  spirits.  Water  dissolves 
about  one-thousandth  of  its 
weight,  which  is  sufficient  to 
communicate  to  it  something 
of  its  peculiar,  pungent,  but 
agreeable  odor.  At  347°  the 
solid  melts,  and  at  410°  it 
boils.  In  the  open  air,  at  ordi-  Lauras  Camphora. 

nary  temperatures,  it.  gradually  evaporates.  When  some  lumps 
of  it  are  contained  in  a  close  glass  vessel,  of  somewhat  larger 
capacity  than  is  merely  sufficient  to  receive  it,  the  vapor  that  forma 
is  gradually  condensed  in  small  crystals  upon  the  side^  of  the 


QUESTIONS. — 649.  What  is  the  composition  of  oil  of  garlic  ?  650.  To 
what  are  the  camphors  allied?  651.  From  what  is  common  camphor 
procured  ?  Describe  its  properties. 


454  VOLATILE    OILS. 

glass ;  and  if  the  vessel  stand  in  a  place  so  that  the  light  can  fall 
<5nly  on  one  side,  the  chief  deposition  will  be  on  the  side  exposed 
to  the  light. 

When  subjected  to  the  action  of  chlorine,  a  part  of  the  hydrogen 
of  the  camphor  is  replaced  by  chlorine,  forming  chlorinated  cam- 
phor, C20H10C]602. 

By  the  action  of  heated  nitric  acid  upon  camphor,  camphoric 
acid,  C20H1608  =  C20H,406,2HO,  is  formed,  which  is  bibasic,  and 
forms  with  alcohol  a  coupled  acid  (609)  and  a  compound  ether. 
By  the  action  of  a  mixture  of  potassa  and  lime,  at  an  elevated 
temperature,  upon  vapor  of  camphor,  another  acid  is  formed,  called 
the  camphoh'c  acid,  the  composition  of  which  is  C2oH,703,HO. 

'  Distilling  this  acid  with  phosphoric  acid,  we  obtain  the  carbo- 
hydrogen,  C,8H16,  called  campholene,  which  is  liquid,  and  boils 
at  275°. 

Borneo  Camphor,  C2oH1802.  —  This  compound  comes  chiefly 
from  the  island  of  Borneo,  and  hence  its  name.  In  some  of  its 
properties  it  closely  resembles  the  preceding,  but  its  odor  and 
taste  are  different.  It  melts  at  383°,  and  boils  at  419°.  In 
composition  it  differs  from  Japan  camphor  only  by  containing 
two  more  equivalents  of  hydrogen*  By  heating  it  with  nitric 
acid,  these  two  equivalents  are  separated  from  it,  and  common 
camphor  formed. 

Coumarine. 

652  By  this  name  a  crystaline,  odoriferous  substance  is  known,  which 
is  extracted  from  the  Tonka  bean,  but  is  also  contained  in  several  plants, 
as  the  sweet  vernal  grass  (anthoxanthum  odoratum).  It  is  procured  by 
digesting  the  bruised  beans  in  strong  alcohol,  which  dissolves  the  odori- 
ferous principle.  Coumarine  is  the  basis  of  the  perfume  called  vanilla. 

By  the  action  of  reagents  it  forms  cdumaric  add,  C18H706,HO. 


QUESTIONS, — What  effect  is  produced  when  common  camphor  is  sub- 
jected to  the  action  of  chlorine?  How  is  camphoric  acid  formed? 
What  is  said  of  Borneo  camphor?  652.  From  what  is  coumarino 
obtained  ?  In  what  perfume  is  it  used  ? 


FIXED    OILS    AND    TATS.  455 


FIXED    OILS    AND    FATS. 

653,  The  fixed  oils  are  so  called  because,  unlike  tlie  essential 
or  volatile  oils,  they  are  incapable  of  being  volatilized  without 
change ;   consequently,  when  spread  upon  paper  they  produce  a 
permanent  stain.     The  fats  are  essentially  the  same  as  the  oils, 
except  that  they  are  usually  solid  at  ordinary  temperatures,  while 
the  oils  are  generally  liquid.     But  the  distinction  is  unimportant. 

Fatty  substances — a  phrase  which  may  include  both  the  fixed 
oils  and  fats — are  found  both  in  the  animal  and  vegetable  king- 
doms ;  and  their  ultimate  elements  are  always  carbon,  hydrogen, 
and  oxygen. 

The  fatty  substance  of  a  plant  is  usually  found  in  the  seeds  or 
pericarp,  occasionally  upon  the  surface  of  the  leaves  or  bark. 
When  contained  in  the  seed  or  pericarp,  it  exists  in  peculiar  cells, 
which  require  to  be  broken  before  it  can  be  separated ;  and  usually 
heat  is  applied  to  render  it  more  liquid,  when  the  separation  is 
effected  by  severe  pressure.  Animal  fats  are  separated  from  the 
tissues  containing  it  either  by  pressure  or  by  the  protracted 
action  of  heat. 

Most  oils  absorb  oxygen  from  the  atmosphere,  by  which  their  con- 
sistency is  changed ;  but  by  some  the  absorption  is  much  more  rapid 
than  by .  others.  Such  as  absorb  oxygen  rapidly — as  linseed  oil — are 
called  siccative,  or  drying  oils,  and  are  used  in  painting.  When  mixed 
with  the  coloring  substance,  or  pigment,  and  spread  upon  the  surface 
of  wood,  or  other  material,  by  means  of  a  brush,  oxygen  is  absorbed  and 
a  resinous  coating  formed,  by  which  the  coloring  substance  is  firmly 
retained.  By  heating  a  drying  oil  nearly  to  the  point  at  which  decom- 
position begins  to  take  place,  the  tendency  to  absorb  oxygen  is  increased. 
This  effect  is  still  greater  if,  before  heating,  some  highly  oxydized  body, 
as  oxide  of  lead  or  manganese,  is  mixed  with  the  oil. 

Unctuous  oils  are  such  as  do  not  absorb  oxygen  from  the  air,  or  do  it 
but  slowly. '  Rancidity  in  oils  is  usually  occasioned  by  the  absorption 
of  oxygen.  Some  oils,  while  they  absorb  oxygen  also  give  off  carbonic 
acid  or  hydrogen. 

654.  Proximate  Principles  of  the  Fats.  —  All  the  fats  and 
fixed  oils  are  composed  of  several  proximate  principles,  which 

QUESTIONS. — 653.  Why  are  the  fixed  oils  so  called  ?  Are  they  found 
both  in  animal  and  vegetable  bodies  ?  In  what  part  of  the  plant  are  they 
usually  found  ?  What  are  siccative,  or  drying  oils  ?  What  are  unctuous 
oils  ?  654.  What  are  the  chief  proximate  principles  of  the  fats  ? 


456  FIXED  OTLS  AND  TATS. 

are  usually  combined  in  definite  proportions.  The  most  common 
of  these  are  glycerine,  stearine,  margarine,  and  oleine,  of  which 
nearly  all  the  animal  fats  and  oils  are  almost  wholly  composed. 
In  several  fatty  substances,  as  butter,  we  find,  in  addition,  small 
quantities  of  other  proximate  principles,  as  butyrine,  caprine,  and 
caproine.  In  some  instances  still  other  principles  are  found, 
which  will  be  described  in  their  proper  places. 

The  proportion  of  stearine,  margarine,  and  oleine  in  the  dif- 
ferent fats  is  exceedingly  variable,  and  occasionally  one  or  another 
of  them  may  be  wanting ;  in  the  more  solid  fats  stearine  and  mar- 
garine are  more  abundant,  while  oleine  is  the  chief  constituent 
of  the  oils  and  more  fusible  fats.  All  of  them  contain  glycerine 
except  spermaceti,  in  which,  instead  of  this  principle,  another 
peculiar  compound  is  found,  called  eihal,  a  substance  in  com- 
position allied  to  the  alcohols. 

The  fats  and  fixed  oils  generally  are  capable  of  combining  with  the 
caustic  alkalies  to  form  soaps,  and  are  therefore  said  to  be  saponifiable. 
The  process  consists  in  digesting  the  fatty  substance  with  a  solution  of  a 
fixed  alkali,  as  potassa,  or  soda,  when  the  stearine,  margarine,  oleine,  &c., 
disappear,  and  corresponding  acids,  called  stearic,  margaric,  oleic,  &c.,  acids, 
are  formed,  which  unite  with  the  alkali,  glycerine  being  at  the  same  time 
get  free. 

These  acids  probably  do  not  exist  as  such  in  the  fats,  or  even  in  the 
proximate  principles  from  which  they  are  derived,  but  are  formed  during 
the  process  of  saponification,  as  will  appear  more  clearly  hereafter.  The 
presence  of  water  is  necessary  to  the  process,  a  small  portion,  of  it,  as 
we  shall  see,  being  required  to  produce  the  compounds  formed. 

Glycerine. 

655.  Glycerine,  C6H806  =  C6H705HO,  was  discovered  by 
Scheele,  and  called  the  "  sweet  principle  of  fat."  It  is  best 
obtained  by  boiling,  for  some  time,  a  mixture  of  equal  parts  of 
olive  oil  and  oxide  of  lead  diffused  in  water,  filtering  the  liquid 
which  remains,  and  then  passing  through  it  a  current  of  sul- 
phuretted hydrogen,  to  separate  all  the  lead.  Lastly,  it  is  heated 
for  a  few  moments  to  the  boiling  point,  and  all  the  water  care- 
fully evaporated  in  a  vacuum. 

QUESTIONS. — In  what  fats  do  stearine  and  margarine  usually  abound  ? 
In  what  is  oleine  the  chief  constituent  ?  What  is  said  of  spermaceti  ? 
What  is  meant  by  the  saponification  of  a  fat  ?  What  are  formed  in  the 
process  of  saponification  2  655.  How  is  glycerine  obtained  ? 


*IXED    OILS    AND    FATS.  457 

As  thus  prepared,  glycerine  is  an  oily  liquid,  very  soluble  in 
water  and  alcohol,  but  insoluble  in  ether ;  quite  inodorous,  but 
having  a  sweet  taste.  Its  specific  gravity  is  about  1-27.  Its 
name  is  derived  from  the  Greek,  ylukus,  sweet,  in  allusion  to  its 
taste. 

With  sulphuric  and  phosphoric  acid  it  forms  coupled  acids  (607) 
similar  to  those  formed  by  these  acids  with  the  alcohols,  which  are 
called  respectively  the  sulphoyly  eerie  and  the  phospliogly  eerie  acids. 

Glycerine  is  not  volatile,  but  is  decomposed  when  heated,  yielding  a 
peculiar,  acrid  volatile  principle,  called  acroleine,  C6H402.  '  It  is  this  sub- 
stance which  constitutes  the  acrid,  irritating  fumes  always  perceived 
when  any  fatty  substance  is  decomposed  by  heat,  in  such  circumstances 
that  the  product  of  the  decomposition  cannot  be  immediately  consumed, 
as  in  the  manufacture  of  gas  from  oil. 

Stearine  and  Stearic  Acid. 

656.  Stearine,  C,42H1400,6.  —  Stearine  (Greek,  stear,  tallow) 
forms  the  chief  constituent  of  tallow,  and  is  a  white  crystaline 
solid,  much  resembling  spermaceti.  It  exists  in  nearly  all  fats, 
and  in  many  of  the  oils,  both  animal  and  vegetable;  and  is  found 
in  greater  proportion  as  the  point  of  congelation  of  the  fat  or  oil  is 
more  elevated.  The  best  method  to  obtain  it  is  to  heat  moderately 
some  mutton  suet  with  8  or  10  times  its  volume  of  camphene,  in 
which  it  will  be  dissolved ;  and,  on  cooling,  the  stearine  will  be 
deposited  in  white  pearly  crystals.  These  are  entirely  insoluble 
in  water,  and  melt  at  140°. 

Stearine,  by  saponification  with  potash,  forms  stearate  of  potash, 
and  hydrated  glycerine  is  set  free ;  and  the  stearate,  by  subse- 
quent decomposition  by  a  mineral  acid,  yields  stearic  acid, 
CwHeA  =  CegHajOg^HO,  which  is  obtained  as  a  white,  crys- 
taline solid. 

Stearic  acid  is  the  substance  of  which  "  stearine"  and  "  ada- 
mantine" candles  are  formed;  and  therefore  constitutes  an  im- 
portant article  of  commerce.  It  melts  at  167°,  and  solidifies  at 
about  158°. 

QUESTIONS. — Describe  the  properties  of  glycerine.     What  is  acroleine? 
656.  What  is  the  derivation  of  the  word  stearine  ?     From  what  is  this 
substance  obtained?     How  is  stearic  acid  formed ?    Describe  it.     What 
use  is  made  of  it  ? 
39 


458  FIXED     OILS    AND    FATS. 

657.  Stearic  acid  for  the  manufacture  of  candles  is  prepared  by  two 
different  processes.     One  method  is  to  digest  the  natural  fat,  as  tallow, 
•with  lime-water,  aided  by  heat,  by  which  an  insoluble  lime-soap  is  formed  : 
and  this  is  then  decomposed  by  dilute  sulphuric  acid,  the  lime  of  course 
all  being  separated,  as  a  sulphate.     The  fatty  acids  now  rising  to  the  top 
are  washed  to  separate  the  glycerine,  and  compressed  to  remove  the  oleic 
and  most  of  the  margaric  acids  ;  and  the  cakeu  of  nearly  pure  stearic  acid 
are  ready  for  use. 

By  the  other  mode  dilute  sulphuric  acid  is  used,  by  which  nearly  the 
eame  effect  is  produced,  this  acid  combining  with  the  glycerine  to  form 
sulphoglyceric  acid  (655),  which  is  washed  away  with  the  water.  The 
fatty  acids  now  obtained  are  distilled,  at  a  high  temperature,  in  an  appa- 
ratus in  which'  a  partial  vacuum  is  kept  up,  and  through  which  a  current 
of  steam  is  continually  passing.  By  pressure  most  of  the  oleic  acid  is 
now  separated,  and  the  mixed  stearic  and  margaric  acids  .obtained. 

The  composition  of  stearine  corresponds  to  2  equivalents  of  anhydrous 
stearic  acid,  and  1  equivalent  of  hydrated  glycerine.  Thus, 

Ci42H140°i6  =  2(0^^0.)  +  C6H706,HO. 

658.  Stearic  ether  is  formed  by  treating  wine  alcohol  with  stearic  acid, 
and  passing  through  the  solution  a  current  of  hydrochloric  acid  ;  and  by 
a  similar  process  with  methylic  alcohol  stearic  methylic  ether  is  formed, 
Both  are  solid  at  temperatures  below  abojut  85°  or  90°. 

Margarine  and  Margaric  Acid. 

659.  Margarine  and  margaric  acid  have  the  same  composition,  respectively, 
as  stearine  and  stearic  acid,  of  which  they  are  isomeric  modifications.    The 
melting  point  of  margarine  is  118°,  and  that  of  margaric  acid  140°. 

660.  Margarone,  CegHegC^,  is  a  white  pearly  substance,  formed  by  dis- 
tilling a  mixture  of  4  parts  of  margaric  acid  and  1  part  of  lime.     The 
following  equation  illustrates  the  chemical  changes  produced  in  the  acid 
to  form  the  margarone^ 


CsgHggOg  -f  2CaO  =  C^H^-}-  2CaO,CO,  -f-  2HO. 

Oleine  and  Oleic  Acid. 

661.  Oleine  is  the  chief  ingredient  of  most  of  the  fixed  oils, 
and  is  found  also  in  many  of  the  fats.  It  is  difficult  to  obtain  it 
pure,  and  therefore  its  formula  cannot  be  given  with  certainty. 

QUESTIONS.-  —  657.  What  two  methods  are  given  for  preparing  stearic 
acid  for  the  manufacture  of  candles?  658.  Describe  stearic  ether. 
659.  What  is  said  of  the  relation  of  margarine  and  margaric  acid  to 
stearine  and  stearic  acid  respectively  ?  660.  What  is  margarone  ? 
661.  What  is  said  of  oleine  ? 


FIXED    OILS    AND    FATS.  459 

It  is  best  prepared  from  olive  oil.  Oleine  is  a  yellowish  liquid, 
of  an  oily  consistency,  which  requires  a  temperature  of  about  zero 
for  congelation. 

Okie  acid,  C36H3303,HO,  is  an  oily  liquid,  having  a  density 
of  about  0-808,  and  solidifies  at  about  32°.  It  is  formed  by 
eaponification  of  oleine,  and  subsequent  decomposition  of  the  soap 
l>y  hydrochloric  acid. 

By  distillation  in  close  vessels  oleic  acid  forms  sebacic  acid,  C]0H803,HO ; 
ffhich,  distilled  with  alcohol  and  hydrochloric  acid,  forms  sebacic  elher. 

Action  of  Nitric  Acid  upon  the  Fatty  Acids. 

662.  Nitric  acid  acts  energetically  upon  the  fatty  acids,  pro- 
ducing a  variety  of  other  acids,  some,  of  which  are  volatile,  and 
others  fixed   at   moderate    temperatures.      The  former  arc  the 
formic,  acetic,  propylic  or  acetonic,  butyric,  valerianic,  caproic, 
ceenanthylic,  caprylic,  pelargonic,  and  capric  acids  ;  all  of  which 
are   homologous,    and   have    the   general   formula,    C2nH2nO4  = 
CA.AjHO. 

At  the  same  time  the  following  non-volatile  acids  are  formed, 
and  may  be  separated  by  the  proper  means,  viz.,  the  succinic, 
adipic,  pimelic,  suberic,  and  sebacic.  These  also  are  homologous, 
and  have  the  general  formula,  C2nH2(n_n08  =  C2nH2(n_2)06,2HO. 

Most  of  these  acids,  it  will  be  observed,  are  also  obtained  from 
other  sources.  The  pelargonic  is  obtained  from  the  rose-geranium 
•(pelargonium  roseum),  the  succinic,  from  amber  (Latin,  SMC- 
cinum),  and  the  suberic,  from  cork,  which  is  the  prepared  bark 
of  the  quercus  suber. 

Other  Proximate  Principles   of  the   Fats,  as   Butyrine,  Pal- 
matine,  &c. 

663.  Butter  contains  several  proximate  principles,  besides  those 
above  described,  as  butyrine,  caprine,   and  caproine,  but  it  is 
difficult  to  separate  them. 

By  digesting  butter  with  an  alkali,  decomposing  the  compound 
formed  by  tartaric  acid,  and  distilling,  butyric  acid,  C8H804  = 

QUESTIONS. — Describe  oleic  acid.  662.  What  is  said  of  the  action  of 
nitric  acid  upon  the  fatty. acids?  663.  What  is  said  of  butter?  How  is 
butyric  acid  obtained  ? 


460  FIXED     OILS     AND     PATS. 

C8H708,HO,  is  obtained,  mixed  with  other  substances,  from 
which  it  is  easily  separated. 

Butyric  acid  may  also  be  formed  from  sugar,  by  mixing  with  a 
solution  of  it  a  little  curds  of  milk  and  powdered  chalk,  and  allow- 
ing it  to  stand  for  a  time  in  a  place  where  it  shall  be  kept  at  a 
temperature  of  about  90°.  A  peculiar  fermentation  takes  place, 
called  the  butyric  fermentation,  and  the  butyric  acid,  as  it  forms, 
combines  with  the  lime,  and  forms  butyrate  of  lime,  which  is 
decomposed  by  hydrochloric  acid,  and  the  butyric  acid  separated 
by  careful  distillation. 

Butyric  acid  is  liquid  at  ordinary  temperatures,  and  boils  at 
about  327°.  Its  density  is  about  0-963,  and  it  is  soluble  in  both 
water  and  alcohol. 

With  alcohol  and  sulphuric  acid  butyric  acid  forms  butyric 
ether,  C4H50,C8ri703.  This  substance,  dissolved  in  5  or  6  times 
its  volume  of  alcohol,  forms  pine-apple  oil,  which  is  used  by  con- 
fectioners for  its  pine-apple  flavor. 

Butyrone,  C7H70,  and  the  compound,  C8H802,  sometimes  called  butyral, 
are  formed  by  distilling  butyrate  of  lime.  Butyral  is  the  proper  alde- 
hyde (547)  of  butyric  acid,  and  may  be  called  butyric  aldehyde. 

Caproic.  caprylic,  and  capric  acids,  are  also  obtained  from  the  decom- 
position of  butter.  Each  of  them  forms  a  vinic  and  a  methylic  ether. 

664.  Castor  oil  (obtained  from  the  plant  called  ricinus  communis) 
by  saponification  forms  ricinoleic  acid,  €33113606=  C38H3505,HO; 
and  this  acid,  distilled  with  solution  of  potassa,  yields  the  com- 
pound, 0|6H,802,  which  is  evidently  homologous  with  the  alcohols, 
and  has  beeo  placed  in  our  list  (547)  as  caprylic  alcohol. 

Palmaline,  and  palmitic  acid,  C94'H^09=CB4'H920&2'HOJ  are  obtained 
from  palni  oil,  which  is  imported  largely  into  this  country  from  the  coast 
of  Africa,  and  used  in  the  manufacture  of  soap. 

665.  Spermaceti — called  also  cetine,  when  pure — is  a  beautiful 
white  substance,  found  mixed  with  oil  in  cavities  of  the  heads  of 
certain  species  of  whales.     The  oil  is  separated  from  it  by  pres- 
sure ;   and  the  hard,  white,  crystaline  substance  thus   obtained 

QUESTIONS. — How  may  butyric  acid  be  formed  from  sugar?  Describe 
its  properties.  How  is  butyric  ether  formed  ?  "What  is  butyrone  ?  What 
is  said  of  butyric  aldehyde  ?  664.  How  is  caprylic  alcohol  procured  ? 
666.  What  is  ethal  ?  From  what  is  it  obtained  ? 


FIXED    OILS    AND    PATS.  461 

melts  at  about  120°,  and  maybe  sublimed  unchanged,  .in  close 
vessels,  at  about  680°. 

Spermaceti  contains  no  glycerine;  but  in  its  place  a  peculiar 
principle  called  etlial,  CaaH^Oa,  is  found,  which  may  be  separated 
as  a  colorless,  crystaline  solid. 

Etlial,  in  many  of  its  properties,  as  has  been  stated,  closely 
resembles  the  alcohols;  and  various  bodies  are  derived  from  it 
gimilar  to  those  derived  from  the  alcohols.  Thus,  when  treated 
with  sulphuric  acid,  it  forms  a  coupled  acid,  called  the  sulpkethalic 
acid,  which  corresponds  to  the  sulphovinic  acid ;  and,  distilled 
with  perchloride  of  phosphorus,  it  yields  a  liquid  ether,  C^^Gl, 
corresponding  exactly  with  the  hydrochloric  ether,  C4H6C1,  pre- 
viously described. 

This  substance  yields  an  acid,  called  the  ethalic,  Ca^J.3204  =  C32TI3,03,  HO, 
corresponding  to  acetic  acid  in  the  common  alcohol  series. 

666.  Wax. — Many  substances,  mostly  of  vegetable  origin,  are 
known  as  wax,  of  which  bees' -wax  is  the  proper  type.     This,  as 
is  well  known,  is  obtained  from  honey-comb,  by  heating  it  with 
water;   the  wax  melts  and  swims  upon  the  surface,  while  the 
impurities  it  contains  are  dissolved  in  the  water,  or  settle  to  the 
bottom.     It  appears  to  be  a  compound  of  two  principles,  cerine 
and  myricine,  which  may  be  separated  by  boiling  alcohol.     Com- 
mon bees'- wax  is  of  a  yellow  color,  but  is  whitened  by  exposing 
it  in  thin  layers  to  the  action  of  the  atmosphere  and  of  light. 

Bayberry  tallow,  or  myrtle  wax,  is  a  fat  obtained  from  the 
fruit  of  the  common  bayberry  (myvica  cerifera).  It  is  obtained 
from  the  berries  by  steeping  them  in  hot  water,  and  is  found  in 
other  vegetables.  Its  composition  is  essentially  the  same  as  com- 
mon tallow,  but  it  contains  other  principles  in  small  quantity, 
among  which  is  myricine.  It  melts  at  117°,  but  is  very  hard 
when  cold,  and  may  be  formed  into  candles. 

667.  Myricine,  C92H9204,  subjected  to  the  action  of  a  boiling 
alkaline  solution,  is  converted  into  palmitic  acid,  C32H3204,  and 

QUESTIONS. — What  is  said  of  the  properties  of  ethal?     666.  From  what 
is  bees'-wax  obtained  ?     What  two  principles  are  mentioned  as  contained 
in  it  ?     From  what  is  myrtle  wax  procured  ?     What  use  is  made  of  it  ? 
66Z    What  is  inelissic  ftlcohol? 
39* 


462  FIXED    OILS     AND    TATS. 

a  compound  called  melissine,  C6oH6202,  which,  being  analogous  in 
composition  to  the  alcohols,  may  be  called  melissic  alcohol. 
Treated  with  potassa  or  lime,  melissic  alcohol  forms  melissic  acid, 
CeaHeA  =  C«,H5903,HO  (547). 

Cerotine,  CwHsAj  and  cerotic  acid,  CMH5404:=  C^Hs-jOgjHO, 
are  other  compounds  obtained  from  wax.  The  former  substanc* 
in  composition .  ranks  with  the  alcohols,  and  may  be  called  ccrotir 
alcohol. 

Soaps  and  Plasters. 

668.  Soaps. — Frequent  allusion  has  already  been  made  to  the 
action  of  the  alkalies  upon  the  fats  and  oils; — when  these  are 
boiled  together,  union  takes  place  between  them,  and  a  well-known 
and  very  important  substance  is  formed,  called  soap.     The  acids 
contained  in  the  fat  or  oil,  as  the  margaric,  stearic,  oleic,  &c., 
described  above,  combine  with  the  alkalies,  forming  proper  salts, 
which  exist  in  the  soap  together  with  other  substances. 

The  soaps  formed  by  potassa,  soda,  and  ammonia  only  are 
soluble  in  water.  Potash  soaps  are  generally  soft,  while  those 
made  with  soda  are  hard  ;  but  their  consistency  depends  also 
upon  the  nature  of  the  fat  used.  All  soaps  contain  a  large  pro- 
portion of  water  in  their  composition. 

Potash  or  soda  for  soap-making  should  be  in  the  caustic  state, 
in  order  to  act  readily  upon  fatty  substances. 

Soft  soaps  are  made  entirely  of  potash  and  tallow  or  oil,  and 
often  other  animal  matters.  For  the  coarser  kinds,  very  impure 
fats  are  used,  without  even  separating  them  from  the  animal 
tissues  in  which  they  are  contained.  The  common  yellow  hard 
soaps  contain  a  portion  of  common  rosin. 

Toilet  soaps  are  often  perfumed  with  the  essential  oils. 

669.  The  mode  in  which  soaps  of  all  kinds  operate  to  produce  their  cleans- 
ing effects  is  easily  understood.     All  soaps  are  always  more  or  less  alkaline, 
as  the  alkalies  contained  in  them  are  not  entirely  neutralized  by  the  oily 
acids  with  which  they  are  combined;  they  are  therefore  ever  ready  to 
combine  with  more  fatty  or  oily  matter  with  which  they  may  come  in 
contact,  as  that  constantly  given  off  in  the  insensible  perspiration  from 

QUESTIONS. — What  is  cerotic  alcohol  ?  668.  How  are  soaps  formed  ? 
What  soaps  are  soluble  in  water  ?  What  are  insoluble  ?  What  are  soft* 
and  what  hard  soaps  ?  669.  Explain  the  action  of  soaps. 


RESINOUS    SUBSTANCES.  463 

the  skin.  Caustic  alkali  always  has  a  soapy  feeling  to  the  fingers,  from 
the  circumstance  that  it  attacks  the  cuticle,  and  forms  with  it  a  soapy 
compound,  at  the  same  time  absorbing  a  portion  of  water  from  the 
atmosphere. 

* 

670.  Plasters.— The  lead-plaster,  or  diachylon,  used  in  surgery,  is  a  kind 
of  metallic  soap,  which  is  made  by  boiling  olive  oil  and  oxide  of  lead 
together,  with  a  little  water.  The  oleic  and  margaric  acids  contained  in 
the  oil  unite  with  the  oxide  of  lead,  in  the  same  manner  as  they  combine 
with  the  alkalies  (oxides  of  potassium  and  sodium)  in  the  formation  of 
soaps.  There  are  two  kinds  of  diachylon,  the  yellow  and  the  brown 
the  former  of  which  is  made  with  litharge,  and  the  latter  with  red  lead ; 
but  their  properties  are  essentially  the  same.  Both  are  quite  hard  at 
ordinary  temperatures,  but  melt  with  a  moderate  heat. 


RESINOUS    SUBSTANCES. 

671.  llesins  are  solid  substances  contained  in  many  plants  and 
trees,  usually  in  a  state  of  solution  in  some  essential  oil.  When 
exposed  to  the  air  the  oil  evaporates,  and  the  solid  resin  is  obtained. 
By  friction  they  usually  become  negatively  electrical.  They  are 
all  insoluble  in  water,  but  most  of  them  are  soluble  in  alcohol, 
ether,  and  the  essential  oils. 

Most  of  them  act  as  weak  acids,  and  are  capable  of  combining 
with  the  alkalies  and  other  metallic  oxides. 

Common  resin,  or  rosin  (French,  colophane),  is  obtained  from 
different  species  of  pine,  in  which  it  exists  combined  with  oil  of 
turpentine.  The  substance  called  turpentine  is  obtained  from 
the  trunk  of  the  tree  by  incisions  made  in  it  while  growing;  and 
this,  by  distillation,  yields  the  oil  of  turpentine,  the  resin  remaining 
behind  in  the  boiler. 

There  are,  in  commerce,  several  different  kinds  of  turpentine,  as 
Venice  turpentine,  Strasbourg  turpentine,  Canada  balsam,  &c. 

When  the  tree  is  felled,  and  the  turpentine  extracted  by  heat,  it  is 
partially  decomposed,  and  acquires  a  dark  color,  and  an  offensive  burnt 
odor,  and  is  called  tar.  By  heating  tar,  so  as  to  expel  all  the  oil  of  tur- 
pentine contained  in  it,  the  common  pitch  of  commerce  is  obtained. 

From  the  different  turpentines,  by  the  action  of-  reagents,  many  im- 
portant substances  may  be  formed,  as  the  pimar'ic,  silvic,  and  pinic  acids. 

672.  Lac,  or  gum  lac,  as  it  is  often  called,  is  procured  from  a 
species  of  tree  called  Jicus,  by  punctures  made  in  the  bark  by 

QUESTIONS. — 670.  How  is  lead-plaster  or  diachylon  formed  ?  671.  What 
are  resins?  What  is  common  resin  or  rosin?  How  is  tat  obtained? 
672.  From  what  is  lac  procured  ? 


464  RESINOUS    SUBSTANCES. 

insects.  It  is  soluble  in  alcohol  and  heated  oil  of  turpentine,  but 
is  quite  insoluble  in  water.  Its  composition  seems  to  be  quite 
complex,  there  being  contained  in  the  common  lac  of  commerce  a 
mixture  of  as  many  as  five  different  resins. 

Lac  is  much  used  in  the  preparation  of  varnish  and  the  manufacture 
of  sealing-wax. 

Copal  is  the  resin  of  the  rhus  copallinum  and  eleocarpus 
copaliferuSj  trees  found  only  in  warm  climates.  It  is  of  a  light 
yellow  color,  and  very  hard,  and  without  odor  or  taste.  Its 
specific  gravity  is  about  1-11.  It  is  believed  to  be  a  mixture 
of  several  different  resins,  which,  by  proper  processes,  may  be 
caparated  from  each  other. 

This  resin  is  quite  insoluble  in  common  alcohol  or  ether,  but  is 
softened,  though  not  dissolved,  by  some  of  the  essential  oils.  Its 
complete  solution  is  effected  by  carefully  fusing  it,  and  then  treating 
it  with  boiling  alcohol  or  oil  of  turpentine. 

Copal  varnish  is  made  by  fusing  the  resin  in  a  deep  copper  vessel,  to 
prevent  it  from  igniting,  and  then  pouring  in  liot  linseed  oil,  and  oil 
of  turpentine,  to  give  the  proper  consistency. 

Mastic  and  sandarac  are  other  resins  used  in  the  preparation  of 
varnishes. 

673.  Amber  (electron  of  the  ancient  Greeks,  and  succinum 
of  the  Romans,)  is  always  found  as  a  fossil,  but  it  appears  to  be 
the  resin  of  some  ancient  tree  that  has  become  extinct.     It  is 
found  on  the  shores  of  the  Baltic  sea,  on  the  Yorkshire  coast 
of  England,  and  in  some  of  the  United  States,  as  in  New  Jersey. 

It  is  found  in  masses  seldom  weighing  more  than  a  few  ounces, 
and  in  small  grains.  Its  color  is  usually  some  shade  of  yellow, 
often  inclining  to  red.  It  has  a  specific  gravity  of  1-07  to  1-09, 
and  is  insoluble  in  water,  and  is  acted  on  but  slightly  by  alcohol, 
ether,  or  the  oils. 

It  is  capable  of  being  worked  in  the  lathe,  and  is  often  seen  fashioned 
into  ornaments  of  various  forms.  It  is  used  also  in  the  preparation 
of  varnishes. 

674.  Caoutchouc. — This  substance,  sometimes  called  gum  elastic, 
or  India-rubber,  is  prepared  from  the  milky  juice  which  exudes 

QUESTIONS. — What  use  is  made  of  lac?  From  what  is  copal  procured? 
What  use  is  made  of  it  ?  673.  Where  is  amber  found  ?  Give  a  description 
of  it.  674.  From  what  is  gum  elastic  obtained  ? 


VEGETABLE    ACIDS.  465 

from  certain  trees,  as  thejicus  elastica,  when  incisions  are  made 
in  them.  The  white  milky  juice  which  exudes  is  received  on 
masses  of  clay,  and  dried  by  exposure  to  the  heat  and  smoke 
of  fires  kindled  for  the  purpose. 

As  usually  seen,  caoutchouc  is  a  solid  of  a  dark  color,  and 
specific  gravity  a  little  less  than  water.  At  32°,  and  lower  tem- 
peratures, it  is  very  hard,  and  has  little  elasticity ;  but  at  60°  or 
70°,  it  is  exceedingly  flexible  and  elastic.  It  is  quite  insoluble 
in  water,  and  alcohol,  but  dissolves  slightly  in  pure  ether  and 
some  of  the  essential  oils.  Chloroform  dissolves  it  readily,  as 
does  also  a  solution  of  sulphur  in  oil  of  turpentine. 

By  distillation  it  yields  several  peculiar  products. 

Vulcanized  India-rubber  is  formed  by  heating  caoutchouc  with  a 
portion  of  sxilphur,  which  becomes  incorporated  with  it,  increases  ita 
elasticity,  and  renders  it  less  liable  to  be  affected  by  changes  of  tem- 
perature. It  is  used  for  many  important  purposes. 

675.  Gutta  Percha  is  a  substance,  in  many  of  its  properties, 
closely  resembling  the  preceding;  it  is  prepared  in  the  same  way 
from  the  milky  juice  of  a  tree  found  only  in  tropical  climates. 

Like  India-rubber^  it  is  quite  insoluble  in  water  and  alcohol, 
but  is  "dissolved  in  small  quantities  by  pure  ether  and  some  of  the 
essential  oils,  and  more  largely  by  chloroform  and  sulphide  of 
carbon.  Its  specific  gravity  is  about  0-97. 

Gutta  percha  is  less  elastic  than  caoutchouc,  and  at  ordinary 
temperatures  is  quite  hard,  but  becomes  soft  at  200°  to  212°, 
and  may  be  formed  into  any  desired  shape.  It  is  becoming  of 
considerable  importance  in  the  arts. 

VEGETABLE    ACIDS    NOT    INCLUDED    IN    THE    PRE- 
CEDING   GROUPS. 

676.  These  acids  are  all  found  ready  formed  in  plants,  a  cir- 
cumstance in  which   they  differ  from  most  of  those  heretofore 
described.     Sometimes  they  occur  in  a  free  state,  but  generally 
they  are  found  in  combination  with  bases. 

• 

QUESTIONS. — Describe  the  properties  of  gum  elastic.  How  is  vul 
canized  India-rubber  prepared  ?  675.  From  what  is  gutta  percha  ob- 
tained ?  Describe  it.  676.  What  is  said  of  the  acids  of  this  group  ? 


466  VEGETABLE    ACIDS. 

677.  Oxalic  Acid,  C4H208  =  C406,2HO.— Oxalic  acid,  in  com- 
bination  with  bases,  is  found  in  many  plants,  especially  in  certain 
species  of  the  sorrel  (oxalis),  and  also  in  certain  minerals.     Ifc 
may  likewise  be  prepared  artificially,  by  digesting  starch,  or  sugar, 
with  nitric  acid,  and  by  other  processes. 

To  prepare  it  artificially,  add,  in  successive  portions,  24  parts 
of  starch  to  144  of  nitric  acid  of  commerce,  diluted  with  10  parts 
of  water,  and  heat  gently  till  the  nitrous  vapors  cease.  When 
the  action  is  over,  set  the  whole  aside  to  crystalize. 

Pure  oxalic  acid  is  a  crystaline  solid,  in  external  appearance 
not  unlike  Epsom  salt,  for  which  it  has  sometimes  been  mistaken. 
It  is  very  soluble  in  water,  exceedingly  sour  to  the  taste,  and 
poisonous.  Its  composition  in  crystals  is  C4H208  +  2HO. 

678.  Salts  of  Oxalic  Acid. — Oxalic  acid  is  bibasic,  and,  as  in 
the  case  of  other  bibasic  acids,  both  equivalents  of  its  basic  water 
may  be  replaced  at  the  same  time  by  a  fixed  base,  or  only  one 
of  them,  producing  the  two  series  of  salts  of  the  forms  2(RO)C406 
and  RO,C406,HO; — RO  being  used  to  indicate  any  base. 

679.  Oxalate  of  lime,  2CaO,C406,  is  found  in  many  plants,  in  the  cells 
of  which  it  may  often  be  detected  in  small  crystals  by  the  microscope. 
The  crystals  when  thus  found,  or  if  formed  by  other  means,  always  con- 
tain" 2. equivalents  of  water  of  crystalization.  *   It  is  very  insoluble.     With 
potash  it  forms  three  salts,  called  the  neutral  oxalate,   2KO,C408,   the 
binozalale,  KO,C406,HO,  and  the  quadroxalate,  the  latter  containing  twice 
as  much  acid  as  the  next  preceding.     The  binoxalate  is  often  used  in 
solution  to  remove  stains  of  iron-rust,  under  the  name  of  salt  of  sorrel. 

Oxalic  acid  forms  with  the  alcohols,  both  coupled  acids  (609)  and  com- 
pound ethers. 

680.  Tartaric  Acid,  C8H6012r=  C8H4010,2HO.— Tartaric  acid, 
in  combination  with  potash,  exists  in  many  fruits,  especially  in 
grapes  and  in  pine-apples.  When  the  expressed  juice  of  the 
grape  is  fermented,  as  in  the  manufacture  of  wine,  this  salt,  in 
an  impure  state,  is  precipitated  upon  the  inside  of  the  cask,  as 
argol,  or  tartar.  From  this  the  pure  acid  is  obtained,  which  is 
a  white  solid,  very  soluble  in  water,  and  of  an  agreeable  acid 
taste. 

QUESTIONS. — 677.  In  what  is  oxalic  acid  found?  How  may  it  be  pre- 
pared artificially?  Describe  its  properties.  678.  What  is  said  of  the 
baits  of  oxalic  acid  ?  679.  In  what  is  oxalate  of  lime  found  ?  680.  In 
What  is  tartaric  acid  found  ? 


*  VEGETABLE    ACIDS.  467 

Tartaric  acid  is  bibasic,  and  forms  two  series  of  salts,  according 
as  one  only  or  both  equivalents  of  its  basic  water  may  be  replaced 
by  the  base. 

There  are  only  two  or  three  important  salts  of  this  acid,  among  which 
the  acid  tartrate  of  potash,  or  cream  of  tartar,  takes  the  first  place.  Its 
composition  is  KO,C8II4Oi0,HO.  It  is  prepared  entirely  from  the  impure 
tartrate,  or  argol,  forming  the  settlings  of  wine-casks  by  repeated  crys- 
talizations  and  filterings. 

By  saturating  a  solution  of  cream  of  tartar  with  soda,  or  carbonate 
of  soda,  a  double  tartrate  of  potash  and  soda  is  formed,  called  Rochelle 
salt. 

681.  Tartar-emetic  is  a  double  tartrate  of  potash  and  oxide  of  antimony, 
which  is  formed  by  boiling  equal  parts  of  cream  of  tartar  and  the  oxide 
in  6  parts  of  water.  It  is  much  used  in  medicine. 

By  the  action  of  heat  upon  tartaric  acid  its  characters  are  changed, 
and  it  is  converted  into  other  acids,  which  are  generally  isomeric  with 
itself,  as  the  metatartaric,  isotartaric,  and  paratartaric  or  racemic  acids. 

With  the  alcohols  tartaric  acid  also  forms  coupled  acids  and  compound 
ethers. 

682.  Citric  Acid,  CI2H80M  =  CI2H50U  +  3HO.— Citric  acid  is 
obtained  chiefly  from  the  lemon  (citron),  but  is  found  in  other 
fruits,  as  the  orange,  currant,  gooseberry,  strawberry,  &c.  When 
pure  it  forms  crystals,  which  are  very  soluble  in  water,  and  have 
an  agreeable  sour  taste.  It  is  used  in  calico-printing,  and  for 
medicinal  and  domestic  purposes. 

To  prepare  citric  acid,  lemon-juice  is  first  saturated  with  lime, 
and  then  the  citrate  of  lime,  so  formed,  mixed  with  several  times 
its  weight  of  warm  water,  is  decomposed  by  sulphuric  acid.  The 
clear  liquid  is  then  drawn  off  and  evaporated  until  the  crystals 
of  citric  acid  are  deposited  as  the  solution  cools. 

Citric  acid  is  tribasic,  and  forms  three  series  of  salts,  according 
as  one,  two,  or  three  equivalents  of  its  basic  water  may  be  replaced 
by  the  fixed  base. 

By  heat  this  acid  is  decomposed,  forming  carbonic  acid  and  other  pro- 
ducts, among  which  is  aconitic  acid,  C4H03,HO,  so  called  because  first 
obtained  from  the  aconitum  napellus:  By  distillation  it  also  yields  the 
itaconilic  and  citraconic  acids. 

Citric  acid  witn  alcohol  forms  two  different  coupled  acids,  and  a  com- 
pound ether. 

QLESTIONS. — What  is  said  of  the  salts  of  tartaric  acid  ?  What  is  cream 
of  tartar?  Rochelle  salt?  681.  Describe  tartar-emetic.  What  acids  iso- 
meric with  tartaric  acid  are  mentioned  ?  682.  From  what  is  citric  acid 
obtained  ?  Describe  its  properties. 


VEGETABLE    ACIDS.  ^ 

683.  Malic  Acid,  C8H6010  =  C8H408,2 HO.— Malic  acid  is.found 
in  many  vegetables,  both  free  and  in  combination  with  bases,  espe- 
cially in  many  fruits  before   coining  to  maturity,  as  the  apple 
(malum),  and  the  plum.      It  is  abundant  in  the  fruit  of  the 
mountain  ash  (sorbus  aucuparia),  and  in  the  stalk  of  the  rhubarb 
or  pie-plant. 

Pure  malic  acid  forms  crystals  which  are  very  soluble  in  water, 
and  which  melt  at  about  181°.  With  alcohol  it  forms  a  coupled 
acid  and  an  ether,  in  the  same  manner  as  other  bibasic  acids. 

By  the  influence  of  heat,  carefully  managed,  it  may  be  .converted  into 
two  other  acids,  which  are  isomeric  with  each  other,  called  the  maleic, 
and  the  paramaleic  or  fumaric  acids.  The  latter  is  also  found  in  some 
plants,  and  in  Iceland  moss. 

684.  Tannic  Acid,  CI6H8012  =  C16H509)3HO.  —  Tannic  acid 

(called  also  tannin),  occurs  in  the  bark  and  leaves 
of  many  trees,  as  the  oak,  chesnut,  and  hemlock^ 
but  is  especially  abundant  in  nut-galls,  which  are 
excrescences  that  form  upon  the  leaves  of  several 
species  of  the  oak. 

To  prepare  it,  nut-galls,  in  coarse  powder,  are  intro- 
duced into  a  funnel,  of  the  form  A,  represented  in  the 
figure,  the  mouth  having  been  loosely  filled  with  a  little 
cotton,  and  pouring  over  them  some  sulphuric  ether  that 
has  been  previously  washed.     The  funnel  is  placed  in  a 
vessel  of  the  form  B,  into  which  the  liquid  gradually  per- 
colates, and  separates  spontaneously  into  two  portions ; — 
the  lower  being  a  solution  of  the  acid  in  water  (a  little 
of  which  was  contained  in  the  ether),  with  the  lighter  and 
nearly  pure  ether  above  it.     The  acid  solution  can  be 
easily  separated;  and  by  evaporation  it  yields  the  tannio 
acid  as  a  solid  mass. 
This  acid  is  soluble  in  water,  and  has  a  peculiar  astringent 
taste.     It  is  a  feeble  acid,  but  forms  salts  with  bases.     With 
salts  of  the  peroxide  of  iron,  it  forms  a  deep  blue  or  black  pre- 
cipitate, which  is  the  basis  of  writing-ink.*     It  forms  an  insoluble 

*  To  prepare  an  excellent  black  writing-ink,  pour  6  pints  of  boiling  rain-water  upon 
6  ounces  of  the  best  nut-galls  in  powder,  and  add  4  ounces  of  gum-Arabic,  and  let  the 
whole  stand  two  days  in  a  wooden  or  earthen  vessel.  Then  strain  the  liquid  and  mix 
with  it  4  ounces  of  clean  copperas,  and  let  it  stand  one  or  two  months,  stirring  it  fre- 
quently, and  pour  off  the  part  free  from  sediment  for  use. 


Prep,  of  Tannic 
Acid. 


QUESTIONS. — 683.  Describe  malic  acid.     684.  In  what  does  tannic  acid 
or  tannin  occur  ?     Describe  the  mode  of  preparing  it. 


ALKALOIDS.  461 

And  very  important  compound  with  gelatine,  which  is  the  basit 
of  leather.  Raw  hides,  after  the  hair  is  removed,  are  soaked  foi 
a  time  in  a  decoction  of  bark  which  contains  this  substance,  and 
are  thus  coanged  into  leather. 

685.  Gallic  Acid,  C14H6010  =  C14H307,3HO.  —  This  acid  is 
usually  associated  with  the  preceding,  and  is  always  formed  when 
a  solution  of  that  acid  is  left  for  some  time  to  the  action  of  the 
atmosphere,  or  is  boiled  for  a  time  with  sulphuric  acid.  In  the 
latter  case,  the  reaction  is  attended  by  the  formation  of  grape- 
sugar.  This  acid  is  readily  obtained  in  crystals,  which  are  quite 
insoluble  in  cold,  but  very  soluble  iu  hot  water. 

By  the  action  of  heat  two  other  acids  are  formed  from  gallic  acid, 
called  the  pyrogallic  and  metagallic  acids. 


ORGANIC    ALKALIES,     OR    ALKALOIDS. 

686.  We  have  seen  above,  that  many  organic  compounds  are 
acids;  so  also  there  are  others  which  are  properly  alkalies,  as 
they  readily,  like  potash,  soda,  &c.,  combine  with  acids  which  they 
neutralize,  forming  true  salts. 

All  the  organic  alkalies  contain  nitrogen  and  hydrogen,  and  in 
some  sulphur  is  found.  Some  of  them  exist  ready  formed  in 
plants,  but  others  are  produced  by  their  destructive  distillation. 

Nearly  all  of  them  are  poisonous. 
» 

687.  Morphia,  or  Morphine,  C34H]8N06. — This  substance  is 
an  essential  ingredient  of  opium,  which  is  the  dried  juice  of  cer- 
tain species  of  the  poppy,  cultivated  largely  in  different  parts  of 
Asia.     To  separate  the  morphia,  the  opium  is  digested  several 
days  in  water,  and  the  solution  precipitated  by  ammonia,  which 
is  added  cautiously  in  small  portions.     The  impure  morphia  thus 
obtained  is  then  further  purified  by  dissolving  it  in  boiling  alco- 
hol, from  which  it  crystalizes  on  cooling. 

The  morphia  in  opium  seems  to  be  in  combination  with  a  pecu- 
liar acid  called  meconic  acid  (from  mecone,  a  poppy). 

QUESTIONS. — What  is  leather  ?  685.  Describe  gallic  acid.  686.  What 
are  the  organic  alkalies  ?  What  is  said  of  their  composition  ?  687.  From 
what  is  morphia  obtained  ?  Describe  the  method  of  separating  it. 

40 


470  ALKALOIDS. 

Pure  morphia  is  a  crystaline  solid,  but  slightly  soluble  in  water, 
and  of  a  bitter  taste.  It  combines  readily  with  acids,  forming  salts, 
the  most  important  of  which  are  the  sulphate,  acetate,  and  hydro* 
chlorate. 

These  salts  are  the  compounds  of  this  substance,  generally  used  in 
medical  practice  under  the  name  of  morphine,  and  not  the  pure  alkaloid, 
which  is  but  slightly  soluble  in  water,  and  therefore  inert.  ^ 

Narcotine  and  codeine  are  other  compounds,  of  a  similar  character, 
procured  from  opium. 

688.  Qninia,  or  Quinine,  CagH^N^. — Quinia  is  obtained  only 
from  the  bark  of  certain  species  of  a  tree  called  cinchona,  which 
grows  chiefly  in  South  America.     In  commerce  it  is  called  Peru- 
vian bark,  and  is  extensively  used  in  medicine. 

To  prepare  quinia,  the  bark,  in  powder,  is  digested  in  waterj 
and  from  the  solution  obtained,  the  alkali  is  precipitated  either  by 
lime  or  ammonia.  The  quinia  may  then  be  dissolved  in  alcohol, 
and  crystalized. 

Quinia  is  a  crystaline  solid,  slightly  soluble  in  water,  and 
intensely  bitter.  It  combines  readily  with  acids,  as  the  sulphuric 
and  hydrochloric ;  and  the  salts  formed  are  extensively  used  in 
medicine,  especially  in  certain  fevers.  With  the  sulphuric  acid 
it  forms  two  salts,  a  neutral  and  an  acid  sulphate. 

689.  Cinchonia,  or  Cinchonine,  C28H24N202. — Cinchonia  always 
accompanies  quinia  in  Peruvian  bark,  and  is  obtained  from  it  by 
a  similar  process.     It  differs  in  composition  irom  quinia,  in  con- 
taining 2  atoms  less  of  oxygen ;   but  in  most  properties,  the  two 
substances  are  much  alike.     Alone,  it  is  but  slightly  soluble  in 
water,  but  the  salts  it  forms  with  acids  dissolve  more  readily,  and 
are  used  in  medicine. 

Quinia  and  cinchonia  exist  together  in  the  bark,  the  former 
being  most  abundant  in  that  which  is  of  a  pale  color,  while  the 
latter  (cinchonia)  occurs  chiefly  in  the  red  bark. 

QUESTIONS. — What  are  some  of  the  properties  of  morphine?  What 
other  alkaloids  are  procured  from  opium  ?  688.  From  what  is  quinia 
prepared  ?  Describe  the  mode  of  separating  it  from  the  bark  ?  689.  In 
what  does  cinchonia  differ  from  quinia  ?  What  is  said  of  the  color  of  tho 
bark  containing  these  alkaloids  ? 


ALKALOIDS    OP    THE    ETHERS.  471 

690.  Strychnia,  or  strychnine,  C42H22N204,  is  a  vegetable  alkali 
obtained  from  nux  vomica,  and  other  plants.     It  is  the  poisonous 
principle  of  the  famous  Upas,  of  the  island  of  Java,  of  which  so 
many  fables  are  told.     It  forms  an  extensive  series  of  salts  with 
the  acids,  and  is  one  of  the  most  violent  poisons  known. 

Brucia,  or  Irucine,  is  a  similar  alkaline  substance,  obtained 
from  the  same  source. 

691.  Isaiine,  Cj6H6N04,  is  derived  from  indigo  by  heating  it  with  dilute 
nitric  acid.     It  is  a  crystalifle  solid,  of  an  orange-red  color,  soluble  in 
hot  water  and  in  alcohol.     From  this  substance  isatinic  acitt  is  derived, 
and  several  other  compounds. 

Theine,  and  Caffeine,  obtained  from  tea  and  coffee,  appear  to  be  the 
same  substance.  It  is  found  also  in  the  fruit  of  some  other  plants,  and 
is  contained  in  larger  quantity  in  tea  than  in  coffee.  It  is  not  certain 
that  these  articles,  so  extensively  used  among  civilized  nations,  owe  their 
peculiar  properties  to  this  principle. 

Nicotine  is  an  alkaloid  obtained  chiefly  from  the  tobacco-leaf.  Piperine 
is  extracted  from  black  pepper ; — it.  is  a  crystaline  solid,  and  acts  as  a 
feeble  base. 

Picrotoxine,  from  the  coculus  Indicus,  cantharadine,  from  cantharides, 
asparagim,  from  the  roots  of  asparagus  and  other  plants,  and  phloridzine, 
from  the  fresh  bark  of  the  apple,  pear,  plum,  and  cherry  trees,  are  com- 
pounds of  a  similar  character. 


ALKALOIDS    OP    THE    ETHERS,    OR    CONJUGATED 
AMMONIAS. 

.692,  The  alkaloids  of  the  ethers,  like  the  ethers  themselves, 
and  the  alcohols,  are  not  found  in  nature,  but  are  produced  only 
by  artificial  means.  They  closely  resemble  ammonia  in  most  of 
their  properties,  and  indeed  may  be  considered  as  ammonia  in 
which  one  or  more  atoms  of  hydrogen  has  been  replaced  by 
equivalent  quantities  of  the  compound  radicals,  ethyle,  C4H5, 
methyle,  C2H3,  acetyle,  C4H3,  &c.  A  few  of  these  only  can  be 
described ;  and  in  doing  so  we  shall  find  it  advantageous  occa- 
sionally to  represent  ethyle,  C4H5,  by  Et;  methyle,  C2H3,  by 
Me;  amyle,  Cj0Hu,  by  Ayl;  acetyle,  C4H8,  by  Ae,  &c. 

QUESTIONS. — 690.  What  is  said  of  strychnia  ?  From  what  is  it  pro- 
cured ?  What  other  alkaloid  accompanies  it  ?  691.  From  what  is  isatino 
obtained  ?  What  is  said  of  theine  and  caifeine  ?  What  other  alkaloids 
are  mentioned  ?  692.  Are  the  alkaloids  of  the  ethers  found  in  nature  ? 
What  do  they  resemble  ?  From  what  may  they  be  considered  as  formed  ? 


472  ALKALOIDS    OF    THE    ETHERS. 

693,  Ethylamine,  C4H7N  =  NH2C4H5  =  NH2Et—  Ethylamine 
is  formed  by  various  processes,  as  by  the  action  of  strong  aqua 
ammoniaB  upon  hydrobromic  ether  (bromide  of  ethyle),  and  then 
distilling  from  potash  or  lime.  The  ammonia  and  ether  are  put 
together  into  a  glass  tube,  which  is  sealed  hermetically,  and  im- 
mersed fifteen  minutes  in  boiling  water;  —  the  reactions  are  as 
follows,  viz.  : 


C4H6Br  +  NH3  =  CJI7N,HBr  =  NH3,C4F5,Br. 

If,  as  intimated  above,  we  consider  ethylamine  a  conjugated 
ammonia,  that  is,  ammonia  in  which  1  atom  of  hydrogen  is 
replaced  by  ethyle,  then  it  is  evident  the  compound,  NH3C4H6  = 
NH3Et,  is  ammonium  in  which  1  atom  of  hydrogen  is  replaced 
by  ethyle.  It  is  called  ethylammonium.  The  compound,  NH3, 
C4H6,Br,  may  therefore  be  called  bromide  of  ethylammonium; 
and  this  when  distilled  with  lime  or  an  alkali  yields  ethylamine, 
precisely  as  sal-ammoniac,  NH4C1,  distilled  with  lime,  yields 
ammonia  (224). 

Ethylamine  is  a  colorless,  limpid  liquid,  having  a  density  of 
about  0-696,  and  boiling  at  about  68°.  It  has  a  pungent  odor 
like  ammonia,  and  alkaline  reaction,  forming  salts  with  acids. 
With  hydrochloric  acid  it  forms  dense  white  fumes,  in  the  same 
manner  as  ammonia. 

694.  By  the  proper  modes,  2,  3,  and  even  4  atoms  of  hydrogen  in  ammonia 
and  ammonium  may  be  replaced,  producing  the  compounds,  biethylamine, 
NH(C4H5)8  =  NHEta,  triethylamine,  N(C4H6)3=NEt3,  and  tetrethylamine, 
N(C4H6)4  =  NEt4.  The  latter,  called  also  telrethylammonium,  like  its 
prototype,  ammonium,  can  only  be  obtained  in  combination,  as  an  iodide, 
bromide,  or  chloride. 

695.  Methylamine,  CaH5N=NHaC2H3=NH2Me.—  This  com- 
pound  is  prepared  in  the  same  manner  as  ethylamine,  simply 
substituting  in  the  process  a  methylic  ether.  It  is  a  colorless 
gas,  having  a  strong  ammoniacal  odor,  and  alkaline  reaction.  By 
a  cold  a  little  below  zero,  it  is  condensed  to  a  limpid,  mobile 
liquid.  In  the  gaseous  state,  it  is  more  soluble  in  water  than 

QUESTIONS.  —  693.  What  is  the  composition  of  ethylamine  ?  What  in 
ethylammonium  ?  Describe  the  properties  of  ethylamine.  694.  What  is 
biethylamine  ?  Triethylamine  ?  Tetrethylamine?  695.  How  is  methyla  - 
mine  formed  ?  In  what  does  it  differ  from  ethylamine  ? 


ALKALOIDS    OP    THE    ETHERS.  473 

any  other  known  gas,  water  at  70°  taking  up  1000  times  its  own 
volume  of  the  gas.  » 


696.  Bimethylamine,  NH(C2H3)2  =  NHMe2,  trimethylamine,  N(C2H3)3  = 
NMe3,  and  tetramethylamine,  N(C2H3)4  =  NMe4,  sustain  the  same  relations 
in  the  methylic  compounds,  as  those  of  corresponding  name,  above  de- 
scribed, in  the  ethyle  series. 


697.  Amylamine,  C10HI9N=NH8C,oH11  =  NH8Ayl.  —  Amy- 

lamine  is  prepared  by  a  process  altogether  similar  to  those  above 
given  for  preparing  the  corresponding  compounds  in  the  ethyle 
and  methyle  series.  It  is  a  limpid  liquid,  which  boils  at  a  little 
above  200°,  and  has  a  density  of  0-750.  It  has  the  odor  of  am- 
monia, and  is  strongly  basic,  forming  salts  with  the  acids. 

Biamylamine,  &c.,  corresponding  to  ethyle  and  methyle  compounds, 
above  described,  are  known. 


698.  Aniline,  C12H7N  =  NH^C^Hg,  is  obtained  from  phenol, 
and  also  by  the  action  of  nitric  acid  upon  indigo.     It  is  an  oily 
liquid,   having  a  density  of  1-028,   and   is  distinctly  alkaline, 
forming  salts  with  the  acids.     It  may  be  considered  as  ammonia 
in  which  1  equivalent  of  the  hydrogen  is  replaced  by  the  group 
C12II5,  called  phenyle.     The  alkaloid  might  therefore  be  named 
plienylamine. 

699.  We  may  even  have  compounds  answering  to  ammonia  iu 
which  the  three  atoms  of  hydrogen  have  been  replaced  successively 
by  different  groups,  or  compound  radicals,  as  in  ethylmethi/lphe- 
nylamine,  N,C2H3,C4H3,C12H5  =  N,MeEt,Pyl. 

700.  In  all  these  compounds,  it  plainly  appears  that  the  groups,  or 
compound  radicals,  ethyle,  C4H5,  methyle,  C2Ii3,  &c.,  are  equivalent  to 
H,  and  replace  it,  in  ammonia,  NH3,  and  ammonium,  NH4.     Now,  phos- 
phorus, P,  is  equivalent  in  combination  to  N;   and  without  experiment 
we  might  expect  P  to  replace  N  in  ammonia,  as  it  does  in  the  compound 
called  phosphuretted  hydrogen,  PH3.      So  a  series  of  compounds  has 
been  discovered,  answering  to  ammonia,  with  its  hydrogen  replaced  by 
the  groups,  ethyle,  methyle,  &c.,  and  the  nitrogen  by  phosphorus.     Thus 
we  have  the  compounds,  P(C2H3)3  =  PMe3,  P(C4H6)8  =  PEt8,  &c. 

QUESTIONS.  —  696.  What  is  bimethylamine  ?     697.  Describe  amylamine. 
698.  Describe  aniline.     Why  may  we  name  it  phenylamine  ?     699.  What 
is  the  composition  of  ethylmethylphenylamine  ?     700.  May  the  nitrogen 
in  these  compounds  be  replaced  by  phosphorus  ? 
40* 


474  ALKALOIDS    OF    THE    ETHERS. 

701.  The  nitrogen  in  these  compounds  may  even  he  replaced 
hy  a  metal,  as  'antimony,  bismuth,  or  tin,  as  in  the  following 
examples. 

Stibethyle,  Sb,C,2H15— Sb(C4H5)3=SbEt3.— Stibethyle  is  pre- 
pared by  the  action  of  hydriodic  or  hydrobromic  ether  upon  anti- 
monide  of  potassium  ]  and  afterwards  distilling  carefully  in  an 
atmosphere  of  carbonic  acid.  It  is  a  transparent,  colorless  liquid 
which  boils  at  317°,  and  has  a  density  of  1'33.  A  drop  of  it 
exposed  in  the  open  air,  first  emits  dense,  white  fumes,  and  then 
takes  fire  spontaneously.  Stibethyle  combines  readily  with  oxygen, 
sulphur,  chlorine,  and  other  elements,  forming  both  binary  com- 
pounds and  proper  salts. 

702.  Stilme-thyle,    Sb(C2H3)3  =  SbMe3,    is    a   corresponding 
compound,   containing    antimony  and    methyle  j    as  is  also    bis- 
raethyle,    Bi(C4H5)3  =  BiEt3,   of  bismuth   and   ethyle.      These 
latter,  and  many  others  of  similar  character,  though  formed  on 
the  type  of  ammonia,  have  less  the  characters  of  ammonia,  and 
react  with  chemical  agents  more  like  simple  metals.     They  are 
therefore  sometimes  called  conjugate  metals. 

All  the  preceding  compounds  have  the  same  molecular  type  as  ammonia 
and  ammonium ;  and  it  is  worthy  of  notice  that  those  having  the  type 
of  ammonium,  like  ammonium  itself,  have  been  obtained  only  in  com- 
bination. 

703.  There  are  other  compounds  similar  in  their  general  characters  to 
the  above,  but  the  molecular  type  of  ammonia  does  not  appear  in  them. 
Of  this  character  are  such  compounds  as  the  following,  viz.,   bisethyle, 
Bi,C4TI6  =  Bi,Et;    zincethyle,   Zn,C4H5=Zn,Et ;    stannethyle,   Sn;C4H5  = 
Sn,Et;   hydrarg ethyle,  Hg2C4H5,  &c.     Each  of  these  (and  many  others) 
combine  with  oxygen,  sulphur,  chlorine,  &c.,  forming  binary  compounds ; 
and  these  again  uniting  with  other  compounds  form  salts. 

704.  Cacodyle,  As,C4H6  =  As,Me2.  —  This  substance  (named 
from  the  Greek,  kakos,  evil,  and  ute,  principle,)  serves  as  the 
basis  of  a  long  series  of  compounds,  in  which  it  performs  the  part 
of  a  quasi-metal.     By  distilling  a  mixture  of  equal  parts  of  acetate 
of  potash  and  arsenious  acid,  we  obtain  a  liquid  substance  long 

QUESTIONS. — 701.  May  the  nitrogen  be  replaced  by  certain  metals? 
What  is  the  composition  of  Stibethyle  ?  Describe  its  properties.  702.  De- 
scribe stibmethyle.  704.  From  what  does  cacodyle  receive  ita  name  ? 


ORGANIC    COLORING-MATTERS.  475 

known  as  Cadet's  fuming  liquid.  Its  composition  is  As,Me2O, 
which  corresponds  to  oxide  of  cacodyle,  but  it  is  more  frequently 
called  akarsine.  When  pure  it  is  a  colorless  liquid,  which  is 
highly  corrosive  and  poisonous. 

According  to  Regnault,  gaseous  alcarsine  has  a  density  of  7-8 ;  by  cal- 
culation we  make  it  7-824.  Its  equivalent,  as  given  above,  represents 
2  volumes,  and  its  density  is  calculated  as  follows: 

4  vols.  carbon  vapor  weigh  (-836  X    4)         3-344 

12     "     hydrogen             "  .    (-069  X  12)           -828 

1     "     arsenic  vapor      "  10-370 

1     "     oxygen                "  1-106 

Thus  giving  for  2  vols.  alcarsine  vapor,.  15-648 

The  weight  of  1  vol.,  or  its  density,  therefore  is    7-824 

705,  Alcarsine,  by  digestion  in  hydrochloric  acid,  is  converted 
into  chloride  of  cacodyle,  AsMe2,Cl,  which  is  decomposed  by  a 
metal,  a«  iron  or  zinc,  and  yields  cacodyle,  As,C4H6,  which  is  a 
colorless,  transparent  liquid,  having  a  density  a  little  above  that 
of  water,  and  boiling  at  about  338°.  In  the  open  air  it  takes 
fire  spontaneously ;  and  even  when  covered  by  a  film  of  water  it 
gradually  absorbs  oxygen  from  the  air,  being  converted  first  into 
akarsine,  As,Me20,  and  then  into  akargen,  or  cacodylic  acidj 
As,Me2,03. 

Cacodyle  forms  important  binary  compounds  with  oxygen,  chlorine, 
sulphur,  &c. ;  and  from  these  many  interesting  salts  are  derived,  not 
here  described. 


ORGANIC    COLORING-MATTERS. 

706.  Color  is  a  property  which  pertains  to  every  substance ;  but 
it  is .  proposed  to  treat  here  of  certain  compounds  noted  for  their 
color,  and  the  practical  us.es  made  of  them  in  the  art  of  coloring. 

Infinite  variety  exists  in  the  colors  of  organic  substances ;  but 

QUESTIONS. — How  is  Cadet's  fuming  liquid  obtained  ?  What  is  it  com- 
posed of?  What  is  it  sometimes  called  ?  What  is  the  density  of  alcarsine 
rapor  ?  705.  What  is  formed  when  alcarsine  is  digested  in  hydrochloric 
acid  ?  How  is  cacodyle  obtained  from  its  chloride  ?  Describe  cacodyle. 
What  is  said  of  the  compounds  of  cacodyle  ?  706.  What  are  to  be  treated 
of  under  the  head  of  organic  coloring-matters  ?  What  is  said  of  the  great 
variety  of  colors  presented  in  nature  ? 


476  ORGANIC    COLORING-MATTERS. 

the  prevailing  tints  are  red,  yellow,  blue,  and  green,  or  mixtures 
of  these  colors. 

707.  The  art  of  dyeing  consists  in  attaching  the  different  color- 
ing-matters to  the  fabrics  to  be  colored.     This  is  accomplished  in 
various  modes,  as  by  adding  some  substance  that  forms  an  inso- 
luble compound  with  the  coloring-matter,  or  one  that  has  the 
property  of  causing  the  coloring-matter  to  attach  itself  perma- 
nently to  the  fibre  of  the  cloth.     A  substance  used  for  this  last 
purpose  is  called  a  mordant. 

As  a  general  rule,  substances  of  an  animal  origin,  as  wool  and  silk,  are 
more  easily  colored  than  those  composed  of  vegetable  matter,  as  cotton 
or  flax. 

Many  coloring-matters  combine  readily  with  certain  of  the  metallic 
oxides,  as  those  of  aluminum,  tin,  &c.,  forming  insoluble  compounds, 
called  lakes,  which  are  much  used  for  painting  in  oils. 

Nearly  all  colors  are  injuriously  affected  by  the  action  of  light;  or,  in 
popular  language,  are  said  to  fade.  This,  it  is  believed,  is  generally 
occasioned  by  the  absorption  of  oxygen,  which  causes  a  decomposition 
of  the  coloring  substance. 

708.  IndigOj   C16H5N02. — This  is  a  beautiful  blue  coloring- 
substance,  extracted  by  a  kind  of  fermenting  process,  from  the 
leaves  of  several  different  American  and  Asiatic  plants,  as  the 
isatis  tinctoria,  pblygonum  tinctorium,  gymnema  tingensj  &c. 

The  leaves  of  the  plant  are  digested  for  eight  or  ten  days  in 
water,  during  which  a  yellow  coloring-matter  appears,  and  is  held 
in  solution  by  the  water.  This  is  then  drawn  off,  and,  by  stand- 
ing, absorbs  oxygen  from  the  air,  and  gradually  becomes  blue,  and 
is  deposited  as  a  thick  sediment.  This  is  collected,  and  pressed 
in  the  form  of  square  blocks,  and  constitutes  the  indigo  o/ 
commerce. 

Indigo  of  commerce  is  far  from  being  pure ; — it  is  a  mixture 
of  indigo  with  other  matters.  Pure  indigo  —  sometimes  called 
indigotine — may  be  obtained  from  it  by  sublimation  with  a  gentle 
heat,  and  by  other  means. 

Pure  indigo  is  an  insipid,  inodorous  substance,  insoluble  in 
water,  but  soluble  in  small  quantity  in  alcohol.  In  strong  sul- 

QTJESTIONS. — 707.  In  what  does  the  art  of  dyeing  consist?  "What  is  a 
mordant?  What  are  lakes?  What  occasions  the  fading  of  colors? 
708.  From  what  is  indigo  obtained  ?  Describe  the  process  of  preparing 
it  What  is  said  of  the  action  of  sulphuric  acid  upon  indigo  ? 


ORGANIC    COLORING-MATTERS.  477 

pliuric  acid  it  dissolves  readily,  with  the  formation  of  several  new 
coupled  acids,  as  the  sulphidigotic,  sulphindylic,  &c.  Alkalies 
act  readily  upon  it,  producing  many  important  compounds,  some 
of  which  have  been  described. 

Deoxydizing  bodies,  as  protosulphate  of  iron,  protochloride  of 
tin,  &c.,  have  the  effect  to  destroy  entirely  the  color  of  the  above 
indigo — called  often  indigo  blue — and  produce  another  compound, 
called  indigo  white.  This  unites  readily  with  bases,  and  forms 
several  soluble  compounds  which  serve  admirably  for  coloring. 
The  solutions,  though  yellowish  at  first,  gradually  become  blue  by 
exposure  to  the  air ;  and  articles  impregnated  with  the  solution 
undergo  the  same  change. 

Solution  of  indigo  in  sulphuric  acid  is  much  used  for  coloring 
the  Saxon  Hue. 

709.  Litmus,  archil,  or  turnsol,  is  a  coloring  substance  resem- 
bling  indigo,   obtained  from  several  species  of  lichen,   as  the 
leconora  parella,  and  the  rocella  tinctoria.     It  is  seen  in  small 
cubical  masses,  which  are  partially  soluble   in   water,   and  the 
solution  communicates  a  beautiful  blue  to  substances  immersed 
in  it.     This  substance  is  much  used  in  chemical  investigations  for 
detecting  the  presence  of  acids  and  bases ;  the  former  of  which 
change  its  blue  color  to  red,  and  the  latter  again  restore  the  blue. 
It  is  a  compound  of  several  principles,  as   lecanorine,  orcine, 
rocelinine,  &c. 

710.  Madder  is  a  red  coloring-substance,  obtained  from  the 
roots  of  a  plant  called  rubia  tinctoria.     It  contains  several  prin- 
ciples, the  most  important  of  which  is  a  red  crystaline  compound 
which  has  received  the  name  alizarine,  CaoHgOg.   "Some  of  the 
other  principles  obtained  from  it  are   madder  purple,  or  pur- 
purine,  C28li]<A5>  madder  red,  C28H909,  and  xanthine. 

By  means  of  different  mordants,  madder  is  made  to  produce 
various  shades  of  red,  purple,  brown,  and  orange.  The  beautiful 
crimson,  called  Turkey-red,  is  produced  by  it  by  means  of  a  corn- 
plicated  process  which  has  not  been  fully  explained. 

QUESTIONS. — What  is  the  effect  of  deoxydizing  bodies  upon  indigo? 
709.  From  what  is  litmus  procured  ?  What  use  is  made  of  it  ?  710.  From 
what  is  madder  procured  ? 


478  AMIDES. 

711.  Cochineal.  —  This  is  a  dried  insect,  which  was  named 
coctus  cacti  by  Linnaeus.     It  is  a  native  of  Mexico,  and  feeds 
upon  a  species  of  the  cactus. 

As  seen  in  commerce,  it  is  of  a  dark  brown,  inclining  to  red, 
but  when  macerated  in  water,  it  yields  a  very  beautiful  red  color- 
ing-matter, which  is  much  used  in  dyeing.  The  beautiful  red 
pigment  called  carmine  is  prepared  from  cochineal  by  boiling  in 
clean  water,  and  adding  a  little  alum ; — as  the  solution  cools,  the 
carmine  is  precipitated,  and  is  collected  and  dried. 

712.  Brezeline  is  a  crystaline  solid,  of  an  orange  .color,  obtained  from 
Brazil-wood,  which  is  soluble  in  water  and  alcohol.     With  mordants,  it 
gives  a  beautiful  red.     The  same  substance  is  contained  in  the  African 
•wood  called  cam-wood. 

Hematoxyline,  C16H708. — This  coloring-matter  is  procured  from  the 
wood  of  the  tree  called  hcemotoxylon  Campeachianum,  and  frequently,  in 
commerce,  log-wood.  It  is  separated  from  the  wood  by  digestion  in 
water,  and  may  be  obtained  in  crystals.  This  substance,  with  salts 
of  iron,  gives  a  permanent  black,  and  with  other  mordants,  different 
shades  of  purple  or  red. 

713.  Quercitrine,  C16H809,HO,  is  a  yellow  coloring-matter,  contained  in 
the  bark  of  the  quercus  tinctoria,  and  probably  in  other  vegetable  sub- 
stances used  in  coloring  yellow.     A  fine  yellow  is  also  produced  by  the 
turmeric  root,  and  by  the  root  of  the  common  barberry  (berberis  vulgaris). 

Chlorophyle. — This  name  has  been  applied  to  the  green  coloring-matter 
of  the  leaves  of  plants.  It  is  contained  only  in  those  parts  of  plants 
which  are  exposed  to  the  light,  and  this  agent  may  therefore  be  supposed 
to  have  an  important  influence  in  its  formation.  It  is  a  substance  of  a 
waxy  nature,  and  is  soluble  in  alcohol,  but  not  in  water. 

The  above  are  the  most  important  coloring-substances  obtained  from 
vegetable  bodies ;  by  their  combination  with  each  other,  and  by  the  use 
of  different  mordants,  in  different  modes,  all  the  endless  variety  of  tints 
are  produced. 

THE     AMIDES     AND     NITRILES. 

714.  Amides. — An  amide  is  a  nitrogenized  compound  answering 
to  a  salt  of  ammonia  less  one  (or  more)  atoms  of  water  (or  its  ele- 
ments).  Thus,  oxamide  (731),  C202,NH2=C203,HO,NH3— 2HO; 
— that  is,  it  answers  to  oxalate  of  ammonia  less  2  atoms  of  water. 
So  benzamide,  C14H7N02  =  C14II502,NH2  =  CI4H503;HO,NH3— 

QUESTIONS. — 711.  What  is  cochineal?  712.  From  what  is  brezelino 
obtained?  What  is  hematoxyline ?  713.  What  is  quercitrine?  Do- 
Bcribe  chlorophyle.  714.  Describe  an  amide. 


AMIDES.  479 

2HO;  —  that  is,  it  answers  to  benzoate  of  ammonia  less  an  atom 
of  water,  or,  less  2  atoms  of  water,  if  we  have  regard  to  the  basic 
water  of  the  salt. 

It  is  also  characteristic  of  the  amides,  that  they  are  capable  of 
resuming  the  water  lost  so  as  to  regenerate  the  ammoniacal  salt  ; 
or  if  a  fixed  alkali  is  used,  a  salt  of  this  alkali  is  formed,  and 
ammonia  set  free.  Thus,  when  benzamide  is  treated  with  a 
boiling  solution  of  potassa,  benzoate  of  potassa  is  formed,  and 
ammonia,  being  gaseous,  escapes. 

715.  The  amides  are  formed  by  several  different  modes,  as  by 
the  simple  distillation  of  a  salt  of  ammonia,  by  the  action  of  aqua 
ammonias  upon  the  compound  ethers,  by  the  action  of  ammonia 
upon  certain  chlorides,  &c.  Oxamide,  for  instance,  is  formed  by 
the  distillation  of  oxalate  of  ammonia,  but  it  may  also  be  pre- 
pared by  the  action  of  aqua  ammonias  upon  oxalic  ether  (616), 
alcohol  being  also  at  the  same  time  reproduced  from  the  ether. 
Thus, 

C4H602,C203  +  NH3  —  C4H602  +  C202,NH2. 


Benzamide  is  usually  prepared  by  the  process  last  mentioned 
from  the  chloride  of  benzyle.     Thus, 


CI4H5C102  +  2NH8:=  C14H602,  +  NH4C1. 

It  is  solid,  and  capable  of  being  crystalized  j  —  at  a  temperature 
of  about  240°  it  melts,  and  at  a  still  higher  temperature  may  be 
sublimed. 

Oxamide  also,  mentioned  above,  is  solid,  and  without  odor  or 
taste.  At  a  high  temperature  it  may  be  sublimed,  but  some  of  it 
will  be  decomposed. 

716.  Malamide,  C8H8N206  =  C8H406,2NH,j,  is  the  amide  of  malic  acid 
(683),  and  is  identical  in  composition  with  asparagine,  a  substance  found 
in  the  young  shoots  of  asparagus,  in  liquorice  root,  and  the  root  of  marsh- 
mallow,  and  in  several  other  plants.  It  may  be  obtained  in  crystals, 
which  require  about  60  times  their  weight  of  water  for  solution.  By  the 
action  of  acida,  it  is  converted  into  ammonia  and  aspartic  acid,  C8H7N08=a 

QUESTIONS.  —  How  may  the  ammoniacal  salt  be  regenerated  ?  715.  What 
are  some  of  the  modes  by  which  the  amides  are  formed  ?  Describe  the 
mode  of  preparing  benzamide.  716.  What  is  malamide,  or  asparagine? 


480  NITRILES.  —  CYANOGEN. 

C8H8N06,2HO.     This  acid  is  also  to  be  considered  as  an  amide,  formed 
from  the  acid  malate  of  ammonia  by  the  loss  of  an  atom  of  water.     Thus, 

C6H408,HO,NH3— HO  =  C8H608,NH2=  C8H6N06,2HO. 

The  above  examples  are  given  as  illustrative  of  the  mode  in  which 
bodies  of  this  class  are  formed,  and  of  their  relation  to  the  ammoniacal 
salts ;  many  are  known  that  cannot  be  here  mentioned.  IMjpst  of  them 
are  neutral  in  their  reactions,  but  they  may  be  acids — as  aspartic  acid — 
or  bases.  Those  that  are  acid,  are  usually  formed  from  acid  salts  of 
ammonia. 

717,  Nitriles, — Many  of  the  amides  are  capable  of  parting  with 
still  another  atom  of  water,  being  then  converted  into  compounds 
called  nitriles.  There  are  not  many  known,  and  they  are  not 
important. 

Acetonitrile,  C4H3N,  is  formed  from  acetamide,  C4H302>NH2, 
by  distilling  the  latter  with  anhydrous  phosphoric  acid,  which 
causes  it  to  Yar^  with  2  atoms  of  water.  Thus, 

C4H302,NH2  —  2HO  =  C4HaN. 

Butyronitrile,  C8H7N,  is  an  oily  liquid,  which  boils  at  about  245°.  It 
is  prepared  by  distilling  butyrate  of  ammonia,  or  butyramide,  with 
anhydrous  phosphoric  acid,  which  separates  an  atom  of  water.  Valero 
nitrile,  C10H9N,  is  obtained  in  a  .similar  manner  from  valerarnide. 


CYANOGEN,  AND  ITS  COMPOUNDS. 

Symbol,  C2N,  or  Cy  5  Equivalent  (12  +  14  =)26;  Density,  1-82 

718,  History. — Cyanogen  has  already  been  mentioned  (315). 
It  was  discovered  by  Gay  Lussac,  in  1814,  and  in  1817  was 
recognized  by  Berzelius  as  a  compound  radical  (536).  In  many 
of  its  properties  it  resembles  chlorine,  bromine,  and  iodine,  com- 
bining like  these  with  other  simple  substances,  and  forming 
compounds  called  cyanides. 

Like  the  elements  above  mentioned,  also,  it  combines  with 
oxygen,  forming  oxacids,  and  with  hydrogen  forming  a  hydracid ; 

QUESTIONS. — Describe  the  mode  of  preparing  aspartic  acid.  Are  there 
acid  and  basic  as  well  as  neutral  amides?  717.  How  are  the  nitriles 
formed?  718.  When  was  cyanogen  discovered ? 


CYANOGEN.  481 

and   in    many  other   respects,    it   reacts   precisely  as   a  simple 

substance. 

719.  Preparation.  —  Cyanogen  may  be  prepared  by  several 
modes.     Its  elements  do  not  combine  directly,  but  a  cyanide  is 
first  formed,  and  this  being  decomposed  yields  the  pure  cyanogen. 
The  best  method  to  procure  a  small  quantity,  is  to  heat  gently  in 
a  small  retort  cyanide  of  mercury,  and  collect  the  cyanogen  over 
mercury.     At  the  same  time  a  brown  mass  will  be  formed,  and 
remain  in  the  retort,  which  has   received  the  name  of  para- 
cyanogen.     It  is  isomeric  with  cyanogen. 

720.  Properties. — Cyanogen  is  a  colorless  gas,  of  a  density 
1-82,  and  has  a  peculiar,  but  not  disagreeable  odor,  resembling 
that  of  wild-cherry  water.     By  a  temperature  of  — 4°,  or  by  a 
pressure  of  4  atmospheres,  at  the  ordinary  summer  temperature, 
it  is  converted  into  a  liquid. 

The  following  method  serves  well  to  prepare  a  small  quantity  in  the 
liquid  form.     Introduce  into  a  strong  glass  tube,  bent  as  in  the  figure, 
a  little  cyanide  of  mercury,  and 
seal  it  hermetically.     It  is  then 
to  be  held  horizontally,  and  the 
heat  of  a  lamp  applied  at  the  ex- 
tremity, a,  containing  the  cyanide  Preparation  of  Cyanogen, 
of  silver.     The  other  extremity,  b, 

is  to  be  kept  cool ;  and  in  a  short  time  the  liquid  cyanogen  will  be  seen 
to  collect  in  it. 

In  the  liquid  form,  cyanogen  is  colorless  and  limpid,  and  has  a  density 
of  about  0-9.  By  long  keeping,  it  undergoes  a  change,  forming  para- 
cyanogen. 

Compounds  of  Cyanogen  and  Oxygen. 

721.  Cyanogen  and  oxygen  -form  no  less  than  three  isomerio 
compounds,  all  of  which  are  acids. 

722.  Cyanic  Acid,  Cy 0,110.  —  Cyanic  acid  is  always  formed 
when  an  alkaline  cyanide,  as  cyanide  of  potassium,  is  exposed  to 

QUESTIONS. — What  simple  substances  does  cyanogen  resemble  in  many 
of  its  properties?  719.  How  is  cyanogen  prepared?  Describe  para- 
cyanogen.  720.  What  are  the  properties  of  cyanogen?  May  it  b« 
obtained  as  a  liquid  ?  May  it  be  preserved  in  the  liquid  form  T 

721.  How  many  compounds  of   cyanogen  and  oxygen    are  known! 

722.  Describe  cyanic  acid. 

41 


482  COMPOUNDS  or  CYANOGEN  AND  OXYGEN. 

the  air  at  a  red  heat ;  oxygen  is  absorbed,  and  the  acid,  as  it  is 
formed,  combines  with  the  alkali.  But  it  is  best  prepared  by 
heating  gently  cyanuric  acid,  a  compound  to  be  hereafter  described. 
It  is  a  clear  transparent  liquid,  with  a  penetrating  odor  not 
unlike  that  of  acetic  acid,  and  is  very  corrosive  to  the  flesh. 

Cyanates. — Cyanate  of  potash  is  prepared  by  heating  the  yellow  prus- 
siate  of  potash  (soon  to  be  described)  with  peroxide  of  manganese,  and 
digesting  the  mass  in  alcohol.  It  is  a  white  crystaline  solid.  Cyanate 
of  ammonia,  which  is  isomeric  with  urea,  is  formed  by  bringing  together 
hydrocyanic  acid  gas  and  ammonia,  and  by  the  action  .of  cyanate  of  pot- 
ash upon  sulphate  of  ammonia.  It  is  also  contained  in  the  urine  of 
animals,  and  is  therefore  called  urea. 

723,  Cyanic  Ether,  C4H50,CyO.—  Cyanic  ether  is  formed  by  distilling 
a  mixture  of  cyanate  of  potassa,  and  the  sulphovinate  (607)  of  the  same 
base.     It  is  a  liquid  less  dense  than  water,  and  has  a  pungent,  irritating 
odor.     Dissolved  in  ammonia,  it  forms  a  crystaline  compound,  CgH8N2Oa, 
which  has  been  called  ammoniacal  cyanic  ether.     When  this  substance  ia 
treated  with  water,  carbonic  acid  is  given  off,  and  a  new  substance 
formed,  called  cyamethene,  having  the  composition,  C10Er,2N202. 

Treated  with  solution  of  caustic  potash,  cyanic  ether  forms  2  equiva- 
lents of  carbonate  of  potash,  and  is  transformed  into  a  new  compound, 
called  ethylamine,  C4H7N  =  NH2,C4HS,  which  in  its  properties  closely 
resembles  the  vegetable  alkaloids  (698). 

724.  Fulminic  Acid,  2CyO,2HO.— Fulminic  acid  has  not  as 
yet  been  obtained  in  a  separate  state,  nor  even  in  combination 
^ith  water.     It  is  formed  by  pouring  alcohol  into  a  strongly  acid 
solution  of  nitrate  of  mercury  or  silver,  and  applying  a  little  heat, 
if  necessary,  so  as  to  produce  brisk  ebullition.     The  acid,  as  it 
forms,  combines  with   the  oxide  of  the    metal  used,   and  the 
metallic  salt,  formed  is  at  once  precipitated.      By  digesting  a 
solution  of  the  metallic  fulminate  with  another  base,  as  potassa, 
the  fulminate  is  decomposed,  and  the  acid  transferred  to  the 
new  base. 

This  acid  receives  its  name  from  the  tendency  of  its  salts  to  explode 
violently  by  heat  or  friction,  or  other  causes. 

Fulminic  acid  is  bibasic,  and,  like  other  acids  of  this  character,  forms 
two  series  of  salts,  the  neutral,  which  contains  2  equivalents  of  fixed 
base  to  each  equivalent  of  the  acid,  and  the  acid  salts  which,  for  each 
equivalent  of  acid,  contain  1  equivalent  of  fixed  base  and  1  equivalent 
of  water. 

QUESTIONS. — What  is  urea?  723.  How  is  cyanic  ether  formed? 
724.  Has  fulminic  acid  been  obtained  in  a  separate  state  ? 


COMPOUND   OP   CYANOGEN   AND   OXYGEN.  483 

725.  The  Fulminates. — There  are  several  fulminates  known, 
but  those  of  mercury  and  silver  are  the  most  important.     The 
former,  fulminate  of  mercury,  is   prepared  by  dissolving  200 
grains  of  mercury  in  an  ounce  of  strong  nitric  acid  by  the  aid 
of  heat,  and,  when  cold,  pouring  into  it  4  or  6  ounces  of  alcohol. 
The  mixture  should  be  contained  in  a  large  glass  or  earthen  vessel, 
and  a  little  heat  applied,  if  the  action  does  not  commence  in  a  few 
minutes  after  adding  the  alcohol.     When   the  action   has  once 
commenced,  it  goes  on  violently,  without  the  further  aid  of  heat, 
attended  by  the  evolution  of  white,  fumes,  consisting  of  aldehyde, 
acetic,  formic,  and  nitrous  acids,  and  their  corresponding  vinic 
ethers,  and  the  deposition  of  the  solid  fulminate  in  small  crystals. 

The  powder  thus  formed  should  be  immediately  well  washed  and  di'ied, 
and  may  then  be  preserved  for  any  length  of  time,  if  kept  in  the  dark, 
but  is  acted  upon  slightly  by  light. 

Fulminate  of  mercury  is  a  brown  crystaline  powder,  without  odor,  but 
having  a  styptic,  metallic  taste.  By  slight- friction  with  any  hard  sub- 
stance, or  by  a  blow,  or  by  the  contact  of  the  minutest  quantity  of  nitric 
or  sulphuric  acid,  it  explodes  with  great  violence ; — even  when  moist,  it 
•will  often  explode  with  a  slight  blow,  and  should  therefore  never  bo 
touched  with  anything  harder  than  wood  or  paper. 

726.  Fulminate  of  mercury  is  much  used  for  fillhig  percussion  caps,  for 
exploding  fire-arms ;  and  for  this  purpose  it  is  mixed  with  a  little  less 
than  half  its  weight  of  nitre,  and  some  solution  of  resin  in  alcohol,  to 
cause  it  to  adhere  to  the  capsule,  and  to  prevent  the  action  of  the  air. 

727.  Fulminate  of  Silver  is  prepared  very  nearly  in  the  same 
manner  as  the  above.  A  dime  is  to  be  dissolved  in  about  2  ounces 
of  common  nitric  acid,  and  the  solution  diluted  with  2  ounces 
of  distilled,  water,  and  then  2  ounces  of  alcohol  abided,  and  the 
whole  mixed  well  by  shaking.  By  application  of  heat,  rapid 
ebullition  will  soon  commence,  when  the  heat  should  be  removed; 
and  the  fulminate  will  be  gradually  deposited,  and  should  be 
immediately  washed  and  dried.  It  is  a  beautiful  white  solid,  and 
should  be  handled  with  the  utmost  care,  as  it  explodes  most 
violently,  even  when  'damp,  by  the  slightest  friction,  or  by  the 
mere  contact  of  sulphuric  acid. 

QUESTIONS. — 725.  Describe  the  mode  of  preparing  fulminate  of  mer 
cury.  Describe  its  properties.  726.  What  use  is  made  of  it  ?  727.  How 
\f  fulminate  of  silver  prepared  ?  What  is  its  character? 


484 


COMPOUNDS    OF  CYANOGEN    AND    HYDROGEN. 


It  is  very  improperly  made  the  basis  of  a  small  toy  called  a  torpedo, 
which  consists  of  a  little  of  the  salt  mixed  with  some  gravel,  and  done  up 
in  paper.  It  explodes  merely  by  being  thrown  upon  a  hard  substance. 

Fulminates  of  copper  and  zinc  may  be  prepared  by  digesting  the  ful- 
minates of  mercury  or  silver  with  these  metals. 

728.  Cyanuric  Acid,  SCyO.SHO.  —  Cyanuric  acid  is  a  white  crystaline 
-olid,  with  little  taste  or  odor,  and  may  be  sublimed  ;  but  a  part  of  it  is 
jy  the  operation  converted  into  cyanic  acid.     It  is  best  formed  by  heating 
irea,  and  digesting  the  mass  in  strong  sulphuric  acid,  adding  a  few  drops 
Df  nitric  acid  until  the  solution  becomes  clear.     To  the  whole  then  add  an 
equal  volume  of  water,  and  as  it  cools  the  acid  will  be  deposited  in  smal 
crystals. 

It  is  a  tribasic  acid,  as  the  above  fonnula  indicates,  and,  like  othei 
tribasic  acids,  forms  with  bases  three  series  of  salts. 
Cyanidide  is  an  isomeric  modification  of  this  acid. 

729.  Cyanuric  Ether,  3C4H50,3CyO,  is  prepared  by  distilling  carefully 
a  mixture  of  the  cyanurate  and  sulphovinate  of  potassa.     It  is  solid  at 
ordinary  temperatures,  but  melts  at  about  185°.  and  boils  at  529°. 

Boiled  for  some  time  with  an  alcoholic  solution  of  potash  it  is  decom- 
posed, yielding  alcohol,  ammonia,  and  carbonic  acid,  according  to  the 
following  equation  : 


3C4H60,3CyO  -f  12HO  =  3C4H602  +  3NH3 


Compound  of  Cyanogen  and  Hydrogen. 

730.  Cyanogen  and  hydrogen  form  one  compound  only ;  which, 
however,  is  exceedingly  important. 

Hydrocyanic  Acid  (Prussic  Acid),  C2N,H,  or  HCy. — Hydro- 
cyanic acid  is  prepared  by  various  processes,  one  of  which  is  to 
A      ^^^^^^^^^^^^5^==^  decompose  cyanide  of 

mercury  by  concen- 
trated hydrochloric 
acid,  by  the  aid  of 
heat.  The  mixed  gases 
are  passed  through  a 
\.  tube  containing  first 
pieces  of  carbonate  of 

Preparation  of  Hydrocyanic  Acid.  f. 

lime,  to  separate  any 

free  hydrochloric  acid,  and  then  fused  chloride   of  calcium  to 
absorb  all  the  moisture;   and  the  hydrocyanic  acid,  mixed  now 


QUESTIONS. — 728.    Describe   cyanuric  acid.      729.    Describe  cyanurio 
730.  How  is  hydrocyanic  acid  prepared  ? 


SULPHOCYANATES.  485 

with  only  carbonic  acid,  is  condensed  in  a  bent  tube,  surrounded 
by  a  freezing  mixture,  the  carbonic  acid  escaping  into  the  air. 

Pure  hydrocyanic  acid  is  a  limpid,  colorless  liquid,  of  a  strong 
odor,  similar  to  that  of  peach-blossoms.  Its  specific  gravity  is 
about  0-70.  Its  point  of  ebullition  is  80°,  and  at  5°  it  congeals. 
When  a  drop  of  it  is  placed  on  a  piece  of  glass,  a  part  of  it  becomes 
solid,  because  th.e  cold  produced  by  the  evaporation  of  a  portion 
is  so  great  as  to.freeze  the  remainder.  It  unites  with  water  and 
alcohol  in  every  proportion. 

Hydrocyanic  acid  is  a  powerful  poison,  producing,  in  poisonous 
doses,  insensibility  and  convulsions,  which  are  speedily  followed 
by  dea-th.  A  single  drop  of  it  placed  on  the  tongue  of  a  dog 
causes  death  in  the  course  of  a  very  few  seconds';  and  small 
animals,  when  confined  in  its  vapor,  are  rapidly  destroyed. 

The  pure  acid  decomposes  spontaneously  when  long  kept,  especially 
if  exposed  to  the  light;  but.  if  largely  diluted  with  water  it  may  be  pre- 
served, and  is  in  this  state  used  in  medicine.  It  is  contained  in  water 
distilled  from  the  blossoms  and  leaves  of  the  peach  and  other  allied 
fruit  trees. 

Sulpliocyanates  or  SulpJiocyan ides. 

731.  The  sulphocyanates  or  sulpliocyanides  constitute   a  class 
of  compounds   corresponding  to  the  cyanates  with   the   oxygen 
replaced   by   sulphur.       Thus    the    composition    of    cyanate    of 
potassa  is  KO,CyO,  while  that  of  the  sulphocyanate  is  KCyS2  = 
KS,CyS. 

732.  Sulphocyanate  of  Potassium,  K,CyS2  =  KS,CyS. — This  is  properly 
a  sulphur  salt.     It  is  obtained  by  making  a  mixture  of  46  parts  of  ferro- 
cyanide  of  potassium,  17  parts  of  pearlash,  and  16  of  sulphur,  and  melting 
them  together ;  and  when  the  whole  has  cooled,  dissolving  out  the  sulpho- 
cyanate by  boiling  alcohol. 

It  is  £  solid,  and  crystalizes  in  long  prisms,  which  are  without  color, 
and  deliquesce  in  the  open  air.  It  is  used  as  a  delicate  test  of  iron. 

733.  Sulphocyanic  Acid,  HCyS2=HS,CyS.—  This  acid,   called  also 
hydrosulpho cyanic  acid,  is  prepared  by  distilling  sulphocyanate  of  potassa 
•with  phosphoric  acid.     It  is  a  colorless  liquid,  .of  a  so.ur  taste,  and  forms 
urith  peroxide  of  iron  salts  of  a  deep  red  color. 

QUESTIONS. — What  are  the  properties  of  hydrocyanic  acid  ?     Is  it  used 
in  medical  practice?     731.  What  is  said  of  the  sulphocyanates  ?    732.  How 
is  sulphocyariiite  of  potassium  formed?     733.  Sulphocyanic  acid? 
41* 


486     COMPOUNDS  OF  CYANOGEN  AND  THE  METALS. 

734.   The  following  compounds  are  derived  mostly  from  the  sulpho- 
cyanates : 

Mellon,  C6N4,  is  a  yellow  insoluble  compound,  obtained  by  distilling  * 
Bulphocyanate  of  potassium  in  an  atmosphere  of  chlorine.  It  is  capable 
of  combining  with  metals,  forming  compounds  which  are  called  mel- 
lonides.  Melam,  C12HUN9,  is  a  grayish-white  powder,  procured  by  de- 
composing, by  heat,  the  sulphocyanate  of  ammonia.  Melamine,  C6H6N6, 
results  from  the  action  of  solution  of  potash,  at  a  bciling  heat,  upor 
melam.  It  is  a  transparent  solid,  scarcely  soluble  in  water,  if  cold,  bu 
very  soluble  in  boiling  water.  When  dry  it  may  be  s.ublimed.  At  th 
same  time  with  the  compound  just  described  is  formed  ammeline,  C6H5N5Oj . 
a  basic  substance,  capable  of  combining  with  the  nitric  and  other  acid&, 
to  form  salts.  It  crystalizes  in  fine  silky  needles.  Ammelide,  C,2HgN906, 
is  formed  by  boiling  ammeline  in  some  acid ; — it  is  a  white  compound, 
insoluble  in  water  and  alcohol,  and  possesses  little  interest. 


Compounds  of  Cyanocfen  and  the  Metals. 

735.  Cyanogen  combines  readily  with  nearly  all  the  metals; 
but  a  few  only  of  the   more  important  of  the  compounds  thus 
formed  can  be  here  noticed. 

736.  Cyanide  of  Potassium,  K,C2N,  or  KCy. — This  compound 
is  best  prepared  by  heating  in  a  covered  crucible  8  parts  of  yel- 
low prussiate  of  potash,  and  adding  three  parts  of  pearlash,  both 
being  first  well  dried.     On  the  large  scale  for  the  manufacture 
of  prussiate  of  potash  above  mentioned,  it  is  prepared  by  heating 
together  in  an  air-furnace  animal  charcoal  and  pearlash.     This 
cyanide  thus  formed,  acting  afterwards  upon  iron,  or  oxide  of 
iron  present,  produces  the  yellow  prussiate  soon  to  be  described. 

Cyanide  of  potassium  is  largely  used  at  the  present  time  in  the  pro- 
cesses of  gilding  and  plating  by  means  of  galvanism. 

737.  Cyanide  of  Mercury,  HgCy,  is  prepared  by  pouring  a  hot  solution 
of  nitrate  of  silver  into  a  hot  concentrated  solution  of  cyanide  of  potas- 
sium, and  purifying,  by  recrystalization,  the  solid  cyanide  of  mercury 
which  is  deposited  when  the  mixed  solution  cools.     It  has  already  been 
mentioned  as  affording  a  ready  means  for  procuring  cyanogen. 

738.  Cyanide  of.  Silver,  AgCy,  is  precipitated  as  a  solid  compound  by 
mixing  hydrocyanic  acid  with  solution  of  any  salt  of  silver.     It  is  inso- 

QUESTIONS.  —  734.  What  other  compounds  are  mentioned  as  derived 
from  the  sulphocyanates  ?  735.  What  is  said  of  cyanogen  in  rela-tion  to 
the  metals  ?  736.  How  is  cyanide  of  potassium  formed  ?  What  use  is 
made  of  it?  737.  What  is  said  of  cyanide  of  mercury?  738.  Cyanide 
of  silver  ? 


DOUBLE  CYANIDES.— POLYCYANIDES.   487 

hible  in  water,  but  is  soluble  in  aqua  ammonia,  and  in  solution  of  nitrate 
of  silver. 

By  modes  altogether  similar  to  the  above,  the  cyanides  of  gold,  zinc, 
cobalt,  nickel,  lead,  copper,  palladium,  &c.,  may  be  procured,  but  the 
compounds  are  not  here  described. 

Double  Cyanides. — Poly  cyanides. 

739.  Nearly  all  the  metallic  cyanides  are  remarkable  for  thei, 
tendency  to  combine  with  each  other,  so  as  to  form  double  cyan- 
ides.    This  is  especially  true  of  the  cyanides  of  iron,  but  many 
others  of  the  class  show  the  same  tendency. 

740.  Hydroferrocyanic  Acid,  FeCy,2HCy  =  H2Cy3Fe.— This 
acid  is  best  prepared  by  mixing  a  saturated  solution  of  yellow 
prussiate  of  potash  with  strong  hydrochloric  acid,  free  from  con- 
tact with  the  air,  and  then  adding  a  small  quantity  of  sulphuric 
ether.     The  acid  is  at  once  precipitated  in  small  white  crystals, 
which  are   to  be  collected  and  dried  in  a  vacuum,  after  being 
washed  with  ether. 

This  acid  may  be  preserved  any  length  of  time  free  from  contact  with 
the  air  and  moisture ;  but  in  the  air  it  is  gradually  decomposed,  leaving 
a  residue  of  Prussian  blue.  It  acts  readily  upon  the  metals  and  metallic 
oxides,  producing*  ferrocyanides. 

741.  Ferrocyanide   of  Potassium.  —  Yellow  Prussiate   of 
Potassa— 2KCy,FeCy,3HO  =  K2Cy3Fe,3HO.  —  This  compound 
is  prepared,  on  the  large  scale,  by  heating  potash  with  animal 
matter,  as  horns,  hoofs,  leather,  woollen   rags,  hair,  and  other 
animal  offal,  by  which  cyanide  of  potassium  is  formed ;   which, 
being  digested. with  warm  water,  containing  fragments  of  iron  or 
smithy  scales,  acts  upon  the  iron  to  produce  the  compound  in 
question.     After  filtering,  the  yellow  Prussiate,  in  solution,  is  set 
aside  to  crystalize.     Instead  of  animal  substances,  as  here  de- 
scribed, common  charcoal  alone  may  be  used  with  the  carbonate 
of  potash,  and  bringing  in  contact  with  it  when  intensely  heated 
atmospheric  nitrogen,  prepared  fey  passing  a  current  of  air  through 
burning  coke. 

QUESTIONS. — 739.  What  is  said  of  nearly  all  the  metallic  cyanides? 
740.  How  is  hydroferi'ocyanic  acid  prepared?  741.  Describe  ferro- 
cyanide  of  potassium. 


488        DOUBLE    CYANIDES. — P  0  L  Y  C  Y  A  N  I  D  E  8. 

Ferrocyanide  of  potassium  is  a  crystaline  solid,  of  a  lemon- 
yellow  color,  very  soluble  in  water,  but  insoluble  in  alcohol  and 
ether.     It  is  much  used  in  the  arts  as  a  coloring  substance,  and* 
as  an  important  reagent  in  the  laboratory  of  the  chemist. 

Many  other  ferrocyanid.es,  as  those  of  sodium,  barium,  calcium,  &&, 
must  be  passed  by  unnoticed, 

742,  Hydroferridcyanic  Acid,  3HCy,Fe8Cy3  =  H8Cy6,Fe8.-- 

This  compound  is  prepared  by  passing  a  current  of  hydro-sul- 
phuric acid  gas  through  a  newly  prepared  solution  of  ferrid- 
cyanide  of  lead.  It  is  obtained  in  crystals,  which  are  soluble  in 
water,  and  have  an  acid,  astringent  taste. 

It  may  be  considered  as  a  compound  of  3  equivalents  of  hydrocyanic 
acid  with  sesquicyanide  of  iron,  as  indicated  by  the  first  of  the  above 
formulae,  or  as  a  compound  of  3  equivalents  of  hydrogen  with  the 
assumed  radical  Cy6Fe2,  as  indicated  by  the  second  formula. 

743,  Ferridcyanide  of  Potassium.— Red  Prussiate  of  Potash, 

3KCy,Fe2Cy3=K3Cy6Fe2- — Red  prussiate  of  potash  is  prepared 
by  passing  a  current,  of  chlorine  through  a  solution  of  the  yellow 
prussiate,  until  it  ceases  to  give  a  blue  precipitate  with  solution 
of  the  persalts  of  iron,  and  evaporating  the  solution  until  crys- 
talization  takes  place. 

The  action  of  the  chlorine  is  to  separate  from  2  equivalents 
of  the  ferrocyanide  one  equivalent  of  potassium,  thus  forming 
chloride  of  potassium  and  the  compound  in  question.  Thus 
2(2KCy,FeCy)  +  01  =  3KCy,Fe2Cy3  +  KC1,  the  water  always 
contained  in  the  crystal  of  the  ferrocyanide  being  omitted. 

The  crystals  beloog  to  the  trimetric  system,  are  of  a  red  color, 
and  readily  burn  when  held  in  the  flame  of  a  candle.  They  are 
partially  soluble  in  cold  and  very  soluble  in  boiling  water,  but 
insoluble  in  alcohol. 

Sometimes,  during  the  process,  the  solution  becomes  green,  by 
the  formation  of  the  magnetic  cyanide  of  iron  (FeCy,Fe2Cy3), 
which,  however,  disappears  by  boiling  with  a  little  caustic  potassa. 

Ferridcyanide  of  potassium  forms  characteristic  colors  with  solutions 
of  several  of  the  metals,  producing  with  them  precipitates  in  which  the 

QUESTIONS. — What  use  is  made  of  ferrocyanide  of  potassium  ?  742.  How 
xnay  hydroferridcyanic  acid  be  procured  ?  Of  what  is  it  composed  ?  743.  De- 
scribe the  red  Prussiate  of  potash.  What  is  said  of  the  colors  produced  by 
this  compound  with  metallic  solutions  ? 


DOUBLE    CYANIDES.  —  jfOLYCYANIDES.         ±89 

potassium  of  the  ferridcyanide  is  replaced  by  an  equal  number  of  equiva? 
lents  of  the  new  metal.  Thus,  with  solution  of  the  protosalts  of  iron  it 
gives  a  blue,  with  those  of  uranium  a  reddish-brown,  with  those  of  nickgl 
and  bismuth  a  brownish-yellow,  and  with  those  of  silver  and  zinc  an 
orange  yellow. 

Similar  compounds  of  sodium,  barium,  calcium,  and  magnesium  are 
known. 

744.  Ferridcyanides  of  Iron,  —  Prussian  Blues.  —  There  are 
several  different  compounds  known  by  these  names.  The  one 
most  common  is  prepared  by  precipitating  an  acid  solution  of 
sulphate  of  iron  with  solution  of  the  yellow  prussiate  of  potash. 
The  compound  thus  formed  is  of  a  deep  blue  color,  uncrystalizafole, 
and  insoluble  in  water  and  alcohol.  When  properly  dried,  it  has 
a  peculiar  metallic,  coppery  lustre,  and  is  much  used  by  painters  ; 
but-  the  color  is  liable  to  fade,  and  is  at  once  destroyed  by  the 
action  of  the  caustic  alkalies  which  decompose  it. 

The  production  of  the  proper  blue  precipitate  in  this  case  requires  the 
presence  of  the  air,  from  which  oxygen  is  largely  absorbed.  When  a 
salt  of  the  peroxide  is  made  use  of,  this  is  not  required. 

The  Prussian  blue  of  commerce  is  very  soluble  in  solution  of  oxalic 
acid,  and  a  good  blue  writing-ink  is  prepared  from  it. 

Prussian  blue  receives  its  name  from  the  fact  that  it  was  first  made  at 
Berlin,  Prussia,  about  the  year  1710.  It  is  sometimes  called  Berlin  blue. 

The  compound  just  described  as  the  ordinary  Prussian  blue  of  com- 
merce, is  probably  a  mixture  of  several  different  cyanides  of  iron. 

Turnbull's  or  Paris  blue,  3FeCy,Fe2Cy3,  is  a  definite  com- 
pound; it  is  best  prepared  by  mixing  a  solution  of  the  red 
Prussiate  of  potash  with  ^solution  of  a  protosalt  of  iron,  the  3 
equivalents  of  potassium  in  the  Prussiate  being  replaced  by  3 
equivalents  of  iron.  Its  color  is  less  intense  but  more  clear  than 
that  of  the  ordinary  Prussian  blue.  Its  formula  may  be  written 
Fe3Cy6Fe2. 

By  precipitating  solution  of  pernitrate  or  perchloride  of  iron 
with  a  solution  of  yellow  Prussiate  of  potash,  a  definite  compound 
is  also  formed  sometimes  called  neutral  Prussian  blue,  or  sesqui- 
ferricyanide  of  iron,  or  hi f err  id  cyanide  of  iron.  Its  composition 
is  3FeCy,2Fe2Cy3.  This  probably  constitutes  the  chief  part  of  the 
common  Prussian  blue  of  commerce. 


QUESTIONS. — 744.  What  is  said  of  the  Prussian  blues  ?  How  may  a 
blue  writing  ink  be  formed  from  Prussian  blue  ?  May  other  Prussian 
blues  be  formed  ? 


490  PROTEINE    COMPOUNDS. 

.  Another  compound,  called  basic  Prussian  Hue,  is  formed  by  pre- 
cipitating a  protosalt  of  iron  with  solution  of  ferrocyanide  of 
potassium,  and  exposing  the  white  compound  thus  obtained  for 
some  time  to  the  action  of  the  air  for  the  absorption  of  oxygen.  * 

Several  other  similar  cyanic  compounds  of  iron  are  known,  called 
soluble.  Prussian  blues,  but  they  cannot  here  be  particularly  described. 

745.  Cobaltocyanides. — Several  other  metals,  as  cobalt,  nickel, 
and  mercury,  enter  into  combination  with  cyanogen,  forming  com- 
pounds in  which  these  metals  perform  essentially  the  same  office 
as  the  iron  in  those  of  the  above  list. 

746.  Hydrocobaltocyanic  Acid,  3HCy,Co2Cy3  =  H3Cy6Co2,   is  obtained 
by  decomposing  cobaltocyanide  of  lead  by  hydrosulphuric  acid,  sepa- 
rating the  sulphide  of  lead  by  filtration,  and  then  evaporating  so  as  to 
crystalize.     The  crystals  thus  procured  are  colorless  and  fibrous,  and 
very  insoluble  in  water.     The  solution  has  a  very  sour  taste,  and  acts 
readily  upon  the  alkaline  carbonates  with  effervescence. 

It  will  be  seen  that  this  compound  corresponds  to  the  hydroferridcyanic 
acid  of  the  iron  series  of  cyanic  compounds.  Like  that  acid,  too,  it 
is  tribasic. 

747.  Cobalticyanide  of  Potassium,  3KCy,Co2Cy3  =  K3Cy6Co2,  is  formed 
by  dissolving  cobalt,  or  its  carbonate,  or  cyanide,  in  solution  of  cyanide 
of  potassium  containing  excess  of  hydrocyanic  acid,  and  evaporating  so 
as  to  crystalize.      It  will  be  noticed  that  the  compound  is  altogether 
analogous  in  composition  to  the  ferridcyanide  of  potassium,  with  which  it 
is  also  isomorphous.     The  crystals  are  of  a  yellowish  color,  and  are  very 
soluble  in  water,  forming  a  colorless  solution. 

Very  many  other  metallic  polycyanides  are  known,  as  the  platino- 
cyanides,  aurocyanides,  argenlocyanides,  merduriocyanides,  &c.,  but -it  would 
extend  our  work  too  much  to  describe  them.- 


ALBUMINOUS,  OR  PROTEINE  COMPOUNDS. 

748.  These  compounds,  three  in  number,  tirejibrine,  albumen, 
and  caseine.  They  are  found  both  in  vegetable  and  animal 
bodies,  and,  like  sugar,  starch,  and  woody-fibre,  are  capable,  in 
certain  circumstances,  of  being  converted  into  each  other.  They 
are  believed  to  be  compounds  of  a  proximate  principle  called 

QUESTIONS. — 745.  What  other  metals  form  cyanides  similar  in  their 
properties  to  those  of  iron?  746.  Describe  hydrocobaltocyanic  acid. 
747.  Describe  cobaltocyanide  of  potassium.  Are  there  other  metallic 
polycyanides  ?  748.  What  are  the  albuminous  or  proteine  compounds  ? 


PEOTEINE    COMPOUNDS.  491 

proteine,  (jproteuo,  I  am  first),  and  having  the  composition, 
C40H3,N50,2.  Its  real  composition,  however,  cannot  be  considered 
as  settled. 

To  obtain  proteine,  albumen  or  caseine  is  to  be  digested  suc- 
cessively in  water,  alcohol,  and  ether,  in  order  to  separate  every- 
thing that  is  soluble  in  these  liquids;  and  the  mass  that  remains 
is  to  be  soaked  for  a  time  in  diluted  hydrochloric  acid,  and  then 
dissolved  in  a  weak  solution  of  caustic  potash.  From  this-,  acetic 
acid,  cautiously  added,  precipitates  the  proteine. 

As  thus  obtained,  proteine  is  a  white,  inodorous  solid,  which  is 
insoluble  in  water  or  alcohol,  and  is  capable  of  forming  different 
compounds  both  with  acids  and  bases.  From  its  acid  compounds 
it  is  readily  precipitated  by  tannic  acid,  with  which  it  forms  an 
insoluble  compound,  by  ferrocyanide  of  potassium,  and  by  the 
alkalies. 

In  the  open  air  it  rapidly  absorbs  moisture,  and  becomes  a  gelatinous 
mass;  and  by  heat  is  decomposed,  exhibiting  the  phenomena  usually 
attending  the  combustion  of  nitrogenized  bodies.  It  leaves  no  residue 
after  combustion. 

749,  Fibrine.— Gluten.— Fibrine  receives  its  name  from  the 
circumstance  that  it  enters  largely  into  the  composition  of  the 
muscular  fibre  of  the  animal  system. 

It  is  best  obtained  by  whipping  a  quantity  of  fresh-drawn  blood 
with  a  bunch  of  twigs,  until  it  coagulates,  and  then  carefully 
washing  with  water  the  stringy  mass  thus  obtained.  Subse- 
quently it  is  to  be  washed  with  alcohol  and  ether,  to  remove  all 
fatty  matter  adhering  to  it,  and  dried. 

When  thus  obtained,  fibrine  is  a  yellowish  opake  mass,  which 
is  quite  insoluble  in  water,  alcohol,  or  ether.  When  long  digested 
in  water,  at  a  very  high  temperature,  a  small  proportion  is  dis- 
solved, but  slight  decomposition  also  takes  place.  It  is  not 
soluble  in  the  acids,  but  dissolves  readily  in  dilute  solutions  of 
tie  alkalies. 

Fibrine,  obtained  in  the  above  manner  from  venous  and  arterial 
blood,  does  not  appear  to  be  exactly  the  same  in  all  its  properties ; 

QUESTIONS. — Is  the  compositipn  of  proteine  known  with  certainty? 
How  may  it  be  obtained  ?  What  are  its  properties  ?  749.  From  what 
does  fibrine  derive  its  name  ?  How  may  it  be  procured  ?  Is  it  th« 
game,  whether  obtained  from  venous  or  arterial  blood  1^ 


192  PEOTEINE    COMPOUNDS. 

AS  that  from  venous  blood,  when  triturated  with  solution  of  nitrato 
of  potash,  at  a  high  temperature,  it  becomes  soluble,  and  very  much 
resembles  albumen,  while  that  from  arterial  blood  is  not  so 
affected. 

Fibrine  may  also  be  obtained  from  the  flesh  of  animals,  of 
which  it  seems  to  form  the  essential  part.  When  procured  from 
this  source,  it  resembles  that  from  venous  blood. 

When  the  juice  of  various  roots,  as  beets,  turnips,  carrots,  &c.,  is 
allowed  to  stand  for  a  time,  a  portion  of  it  coagulates  very  much  like 
blood,  and  may  be  separated  from  the  uncoagulated  part.  It  has  been 
called  vegetable  fibrine,  and  seems  to  be  the  same  as  fibrine  of  animal 
origin. 

750.  Gluten  is  a  substance  obtained  from  the  cereal  grains 
It  may  be  procured  readily  from  wheat  flour  by  kneading  (554)  it 
for  some  time  in  a  large  quantity  of  cold  water,  to  wash  away  all 
the  starch  and  other  products,  and  then  boiling  for  a  time  in 
alcohol.     A  soft,  adhesive,  elastic  mass  is  thus  obtained,  which 
appears  to  be  identical  with  fibrine.     It  is  to  this  substance  that 
wheat  flour  (which  contains  20  or  25  per  cent,  of  it)  owes  its 
adhesive,  plastic  nature  j  and  it  is  this  substance  also,  in  a  state 
of  decomposition  —  mixed,   probably,  with   starch   in  the  same 
state — which  constitutes  yeast. 

751,  Albumen. — This  compound  is  found  nearly  pure  in  the 
whites  of  eggs,  from  which  it  derives  its  name.     Like  fibrine,  it 
exists  in  two  states — as  a  liquid,  in  the  whites  of  eggs,  serum 
of  the  blood,  humors  of  the  eye,  &c. — and,  as  a  solid,  in  the  brain 
and  nerves  of  animals,  and  in  the  seeds  of  plants.     The  latter, 
called  vegetable  albumen,  is  considered  as  altogether  identical  with 
that  of  animal  origin. 

Liquid  albumen  may  be  coagulated,  or  solidified  in  various 
ways,  as  by  heating  to  a  temperature  of  140°,  or  more,  or  by  the 
action  of  chemical  reagents,  as  alcohol,  tannic  acid,  corrosive  sub- 
limate, and  creosote  j  but  when  once  coagulated  it  cannot  be  re- 
dissolved.  As  it  forms  an  insoluble,  and  therefore  inert  com- 
pound with  corrosive  sublimate,  it  is  considered  a  good  antidote 
in  cases  of  poisoning  with  the  latter  substance. 

QUESTIONS. — What  is  said  of  the  juice  of  certain  roots,  as  those  of  beets, 
turnips,  &c.  ?  760.  What  is  gluten?  What  is  yeast?  751.  Describe 
albumen. 


PROIEINE    COMPOUNDS.  493 

Vegetable  albumen  is  found  in  the  leaves  and  stalks  of  plants,  and  in 
the  seeds,  and  in  some  cases  in  the  roots.  As  obtained  from  plants,  it  is 
sometimes  white,  but  is  often  colored.  It  is  contained  in  considerable 
quantity  in  wood,  and  has  great  influence  in  causing  its  decay.  It  is 
therefore  found  that  wood  which  has  been  saturated  with  a  solution  of 
corrosive  sublimate  is  rendered  more  lasting  when  subjected  to  the 
influence  of  the  atmosphere  and  moisture  (501). 

752.  Caseine.— Legumine.— Caseine  in  many  of  its  properties 
closely  resembles  albumen.  It  is  most  readily  obtained  from 
milk;  and  derives  its  name  from  caseum,  curd.  A  very  little 
eulphuric  acid  stirred  in  some  skimmed  milk  causes  it  to  coagu- 
late in  a  short  time;  and  the  curds  so  formed  being  well  washed 
with  water,  and  digested  for  a  time  with  carbonate  of  baryta  to 
separate  the  acid,  afford  the  pure  caseine.  When  dried  it  is  but 
slightly  soluble  in  water,  but  very  soluble  in  solutions  of  the  alka- 
lies, or  alkaline  carbonates. 

Legumine,  believed  to  be  identical  with  the  caseine  from  milk, 
is  procured  from  peas,  beans,  and  other  similar  seeds,  by  bruising 
them  in  water,  and  straining  through  a  fine  sieve;  the  liquid 
which  passes  through  is  a  solution  of  this  substance,  and  contains 
some  starch,  which  settles  by  standing.  The  supernatant  liquid, 
being  poured  off,  possesses  all  the  characters  of  skimmed  milk, 
and  from  it  the  legumine,  or  vegetable  caseine,  may  be  procured 
in  the  same  manner  as  from  milk. 

Caseine,  in  milk,  is  held  in  solution  by  free  alkali  present ; — 
it  is  not  coagulated  by  heat,  like  albumen,  but  coagulates  readily 
by  the  action  of  rennet,  or  by  acids,  except  the  phosphoric. 

The  three  important  compounds  above  described  very  closely  resemble 
each  other  in  many  of  their  properties,  as  well  as  in  composition ;  but 
they  are  at  the  same  time,  in  other  properties,  essentially  different. 
Fibrine  coagulates  spontaneously  by  standing,  but  the  other  two  undergo 
this  change  only  by  the  application  of  certain  agents.  Albumen  is  not 
coagulated  by  acids,  nor  by  rennet,  but  coagulates  by  heat,  by  contact 
of  alcohol,  and  some  of  the  metallic  salts,  and  other  compounds.  Caseine 
does  not  coagulate  by  heat,  nor  by  alcohol,  but  is  readily  coagulated  by 
most  of  the  acids,  and  by  rennet.  Probably  what  is  considered  as  liqtiid 
caseine  is  only  the  substance  held  in  solution  by  an  alkali;  and  the 
coagulation  of  it  by  an  acid  results  from  the  neutralization  of  the  alkali 
by  the  acid. 

QUESTIONS. — In  what  parts  of  plants  is  vegetable  albumen  contained  ? 
752.  Describe  caseine.     Describe  legumine.     How  is  caseine  coagulated  ? 
How  are  fibrine  and  albumen  coagulated? 
42 


494  PHENOMENA    OF    VEGETATION. 

Each  of  these  substances  appears  always  to  contain  a  small  quantity 
of  sulphur ;  and  fibrine  and  albumen  contain,  in  addition,  a  little  phos- 
phorus. Decomposed  by  heating  wifh  acids  or  other  reagents,  they  afford 
very  complex  results. 

When  kept  for  a  time  they  undergo  spontaneous  decompostion,  and  in 
certain  circumstances  also  induce  peculiar  changes  in  other  organic  com- 
pounds, as  in  the  production  of  the  alcoholic  and  other  fermentations. 

Being  so  nearly  the  same  in  composition,  if  not  absolutely  identical,  it 
is  altogether  probable  that,  both  in  vegetables  and  animals,  frequent 
transformations  of  one  of  these  substances  into  another  take  place,  by 
means  and  processes  not  yet  understood. 


CHEMICAL  PHENOMENA  OF  VEGETATION. 

753.  Germination  is  the  process  by  which  a  new  plant  ori- 
ginates from  seed.  A  seed  consists  essentially  of  two  parts,  the 
germ  of  the  future  plant,  endowed  with  a  principle  of  vitality, 
and  the  cotyledons,  or  seed-lobes,  both  of  which  are  enveloped  in  a" 
common  covering  or  cuticle.  In  the  germ  two  parts,  the  radicle 
and  plumula,  may  be  distinguished,  the  former  of  which  is  des- 
tined to  descend  into  the  earth  and  constitute  the  root,  the  latter 
to  rise  into  the  air  and  form  the  stem  of  the  plant.  The  office 
of  the  seed-lobes  is  to  afford  nourishment  to  the  young  plant  until 
its  organization  is  so  far  advanced  that  it  may  draw  materials  for 
its  growth  from  extraneous  sources. 

The  conditions  necessary  to  germination  are  threefold ;  namely, 
moisture,  a  certain  temperature,  and  the  presence  of  oxygen  gas. 
The  necessity  of  moisture  to  this  -process  has  been  proved  by 
extensive  observation.  It  is  well  known  that  the  concurrence 
of  other  conditions  cannot  enable  seeds  to  germinate  provided 
they  are  kept  quite  dry. 

A  certain  degree  of  warmth  is  not  less  essential  than  moisture. 
Germination  cannot  take  place  at  a  very  low  temperature;  and 
a  high  temperature,  as  that  of  boiling  water,  destroys  the  vitality 
of  the  seeds.  The  most  favorable  temperature  for  the  germination 
of  most  seeds  is  between  60°  and  80°. 

In  the  process  of  incipient  germination  a  kind  of  saccharine  fermenta- 
tion (556)  takes  place,  by  which  nutriment  is  supplied  for  the  young 

QUESTIONS. — 753.  What  are  the  essential  parts  of  a  seed?  Describe 
the  process  of  germination  in  a  seed  ?  What  are  the  conditions  required 
for  healthy  germination  ? 


PHENOMENA    OF    VEGETATION.  495 

plant  during  the  early  stages  of  its  growth.  This  seems  to  be  occasioned 
by  the  influence  of  the  active  principle  diastase,  which  is  not  pre-existent 
in  the  seed,  but  is  formed  by  the  action  of  the  air  and  moisture  on  the 
substances  contained  in  it.  When  the  process  of  germination  is  over,  the 
plant  is  found  provided  with  the  necessary  organs  for  procuring  its  nutri- 
ment from  the  atmosphere  and  soil ;  and  there  remains  of  the  seed  only 
its  ligneous  husk,  which  sometimes  perishes  in  the  ground,  but  at  others 
rises  to  the  surface  and  performs  for  a  time  the  functions  of  leaves, 

754.  Respiration  of  Plants.  — Assimilation  of  Carbon.  —  We 
have  already  noticed  (213)  the  beautiful  provision,  by  which  the 
two  great  classes  of  organized  bodies  mutually  compensate  for  the 
change  each  produces  in  the  constituents  of  the  atmosphere,  and 
continue  that  proportion  of  them  which  is  conducive  to  the 
healthful  existence  of  both.  Animals,  by  respiration,  are  con- 
stantly giving  off  carbonic  acid,  while  plants,  by  the  action  of 
light  upon  their  leaves,  absorb  carbonic  acid  and  exhale  oxyg^p. 

It  will  be  seen,  therefore,  that  a  process  is  ever  going  on  in 
plants — at  least  when  under  the  influence  of  light — not  unlike 
the  respiration  of  animals,  in  which  the  leaves  perform  the  office 
of  lungs.  But  the  changes  produced  in  the  atmosphere  being  the 
rfverse  of  those  occasioned  by  the  respiration  of  animals,  the  two 
processes  serve  to  support  each  other;  and  the  proportional- 
quantity  of  oxygen  and  carbonic  acid  in  the  atmosphere  is  pre- 
served ever  the  same. 

The  carbon  obtained  by  plants  by  this  respiratory  process,  and  the 
water  which  is  absorbed  by  the  roots  and  leaves,  furnish  the  elements 
of  woody  matter,  and  other  substances,  as  sugar,  starch,  gum,  &c., 
which  contain  oxygen  and  hydrogen  in  the  proportion  to  form  water. 
But  the  actions"  that  really  take  place  are  usually  much  more  complex 
than  this  would  seem  to  indicate.  The  absorption  of  carbonic  acid,  and 
the  liberation  of  oxygen,  take  place  only  in  the  light;  in  the  dark,  an 
opposite  process  sets  in — oxygen  is  absorbed  and  carbonic  acid  is  given 
off.  But  it  has  been  well  established  that,  on  the  whob,  the  quantity 
of  carbonic  acid  absorbed  is  much  greater  that  that  evolved,  whilst  the 
quantity  of  oxygen  evolved  is  much  greater  than  that  absorbed.  Very 
many  plants,  it  is  believed,  receive  a  large  part  of  the  carbon  they  con- 
tain from  the  atmosphere,  while  some  few  probably  receive  the  whole. 
Others  derive  a  part  from  the  soil. 

Now  it  is  not  difficult  to  trace  some  of  the  further  changes  which  no 
doubt  take  place  in  the  plant.  All  the  softer  parts  of  most  plants  con- 

QUESTIONS. — 754.  What  is  meant  by  the  respiration  of  plants  ?  What 
different  effects  are  produced  upon  the  atmosphere  by  the  respiration 
of  plants  and  animals  ?  Does  the  absorption  of  carbonic  acid  take  place 
op^y  in  the  light  ? 


496  PHENOMENA    OP    VEGETATION. 

tain  abundance  of  starch  ;  even  in  the  tubes  and  cells  of  ordinary  wood 
it  is  found.  This  is  so  closely  allied  to  sugar,  gum,  and  woody-fibre,  and 
the  transformations  of  them  from  one  to  another  so  easy,  that  we  may 
suppose  them  to  be  constantly  taking  place. 

The  other  numerous  secondary  products,  as  the  vegetable  acids,  oils, 
coloring-matters,  &c.,  which  characterize  plants,  may  be  formed  from 
starch  during  the  inverse  respiratory  action  just  alluded  to,  in  which 
carbonic  acid  is  given  off,  and  oxygen  absorbed  from  the  atmosphere. 
During  the  day  the  assimilating  power  of  the  plant  is  in  action,  and  car- 
bonic acid  is  rapidly  absorbed,  and  oxygen  evolved ;  but  during  the 
night,  while  the  plant  is  in  repose,  this  nutritious  action  ceases,  and  a 
different  process  commences,  during  which  the  various  substances  natural 
to  the  plant  are  elaborated,  attended  by  the  absorption  of  oxygen  from 
the  atmosphere,  and  the  evolution  of  carbonic  acid  and  water.  This 
change  is  well  illustrated  by  certain  plants,  as  the  cacalia  ficoides,  the 
leaves  of  which  are  bitter  in  the  evening,  but  in  the  morning  are  sour, 
like  those  of  sorrel.  During  the  night  oxygen  has  been  absorbed,  and 
an  acid  generated  from  materials  that  were  combined  the  evening  previous, 
in  a  different  mode. 

Nitrogen  is  an  essential  ingredient  in  many  of  the  products  of  plants ; — 
it  is  believed  to  be  obtained  chiefly  from  the  soil. 

755,  Inorganic  Constituents  of  Plants. — Besides  the  sub- 
stances which  form  Jhe  organic  matter  of  plants,  various  inor- 
ganic bodies,  as  alkaline  and  earthy  salts,  are  usually  found 
contained  in  them,  and  no  doubt  serve  an  important  purpose. 
If  a  plant  is  made  to  vegetate  in  a  soil  containing  in  it  small 
quantities  of  several  salts,  we  find  that,  while  it  continues  in 
health,  it  seems  to  exercise  a  remarkable  discretionary  power, 
absorbing  some,  and  rejecting  others.  Those  absorbed  most 
freely  are  such  as  are  required  for  its  proper  growth,  and  are 
not  given  up  to  the  water  in  which  the  plant  may  be  immersed ; 
while  some  are  absorbed  and  again  given  off,  and  others  still 
are  entirely  rejected,  as  being  injurious.  Most  plants  contain 
a  small  quantity  of  some  salt  of  potassa,  which  exists  as  a  car- 
bonate in  the  ashes  resulting  from  their  combustion ;  but  plants 
that  grow  near  the  sea,  or  springs  of  salt  water,  usually  contain 
soda  instead  of  potassa.  Silica,  lime,  magnesia,  &c.?  are  also 
often  contained  in  plants. 

As  these  inorganic  substances  are  necessary  for  the  proper  growth 
of  plants,  and  all  plants  do  not  require  the  same  substance,  it  is  plain 
that  a  particular  plant  can  be  expected  to  flourish  only  in  soils  containing 
the  substances  it,  requires. 

QUESTIONS. — Is  nitrogen  assimilated  by  plants?  From  what  is  it 
derived  ?  755.  What  are  the  inorganic  constituents  of  plants  ?  Do  dif 
ferent  plants  absorb  very  different  substances  from  the  soil  ? 


PHENOMENA    OF    VEGETATION.  497 

756.  Nature  and  Use  of  Manures. — Every  substance  is  called 
a  manure  which,  applied  to  a  soil,  increases  its  productiveness. 
In  a  particular  case  it  may  be  a  substance  which  is  required  in 
the  proposed  crop,  but  of  which  the  soil  is  deficient ;  or  it  may  be 
a  substance  designed  merely  to  give  the  soil  a  proper  texture,  so 
that  it  may  more  easily  be  penetrated  by  the  rootlets  of  the  plants, 
or  to  increase  its  adhesiveness  and  enable  it  to  retain  longer  the 
moisture  that  falls  upon  it.     It  is  in  the  manner  last  mentioned, 
probably,  that  most  mineral  manures,  as  lime,  marl,  &c.,  usually 
operate.  * 

From  the  preceding  remarks,  the  great  advantage  of  rotation 
of  crops  may  readily  be  seen.  The  mineral  constituents  of  a  soil 
are  derived  from  the  disintegration  of  its  subjacent  rocks;  and 
some  of  them  being  contained  only  in  small  quantities,  by  con- 
tinued succession  of  the  same  crop,  may  be  entirely  removed,  and 
the  soil  become  impoverished.  By  substituting  another  crop, 
which  requires  little  or  none  of  the  material  which  has  been 
exhausted,  an  abundant  harvest  may  be  obtained ;  and  the  soil, 
by  the  gradual  decomposition  of  its  subsoil,  recover  its  former 
constitution. 

757.  The  great  value  of  organic  manures  is  supposed  to  depend  almost 
entirely  upon  the  nitrogen  they  supply  to  the  soil.      The  most  of  the 
nitrogen  in  plants  is  contained  in  the  seed,  tubers,  &c.,  those  parts  which 
are  selected  by  man  for  food,  or  for  medicinal  purposes,  in  consequence 
of  the  active  principles  they  contain ;  and  but  little  is  found  in  the  stem, 
leaves,  root,  &c.,  which  are  rejected  as  useless.     The  residue  of  a  former 
season,  therefore,  may  manure  the  land  abundantly,  so  far  as  carbon  is 
concerned,  but  there  will  be  a  deficiency  of  nitrogen,  an  essential  ele- 
ment of  the  future  desired  crop.      This  deficiency  is  supplied  by  the 
decaying  animal  and  vegetable  substances  used  as  manures ;  the  value 
of  which  will  therefore  be  very  nearly  in  proportion  to  the  nitrogen  they 
supply.     If  mere  ammoniacal  salts  are  used,  or  perishable  animal  sub- 
stances, their  whole  benefit  is  imparted  to  the  crop  immediately  succeed- 
ing their  application;   but  organic  substances,  which  decay  but  slowly, 
yield  a  more  permanent  benefit :  their  nitrogen  is  gradually  evolved,  and 
though  little  benefit  at  first  appears,  the  soil  is  at  length  found  to  be 
essentially  improved. 

758.  In  healthy  vegetation,  light  serves  a  most  important  purpose; 
indeed,  without  it,  no  plant  could  come  to  perfection.     A  plant  which 
grows  in  darkness,  as  in  a  cellar,  however  rich  may  be  the  soil  in  which 

QUESTIONS. — 756.  What  are  manures?     Explain  the  different  modes  in 
which  manures  operate  to  produce  their  effects?     758.  What  is  said  of 
the  importance  of  light  to  healthy  vegetation? 
42* 


498  ANIMAL    TISSUES.      . 

it  stands,  remains  soft,  its  color  pale,  and  its  woody  fibre  unformed. 
"When  brought  to  the  light,  it  perhaps  increases  in  volume  less  rapidly, 
)>ut  the  healthy  action  of  the  organ  at  once  commences ;  the  green  color 
appears,  and  all  the  parts  of  the  plant  begin  gradually  to  advance  to 
maturity. 
* 

COMPOSITION    OF    THE    ANIMAL    TISSUES. 

759.  By  the  animal  tissues  we  understand  all  the  various  solid 
found  in  the  system,  not  excepting  the  bones  and  teeth. 

The  Muscles. — The  muscles  are  the  organs  of  motion  to  the 
animal,  and  they  act  solely  by  their  contractions,  which  take 
place  at  the  will  of  the  animal.  Their  structure  is  always  fibrous, 
and  in  the  mammalia  they  are  of  a  red  color,  and  receive  from 
the  circulation  a  large  supply  of  blood.  The  chief  substances 
contained  in  them  are  fibrine,  albumen,  and  gelatine.  The  two 

latter  substances  are  con- 
tained chiefly  in  the 
membranes  which  en- 
velope the  fibres. 

The  accompanying  fig- 
ure represents  a  piece  of 
muscle,  and  shows  its 
fibrous  structure.  When 

Piece  of  Muscle. 

taken   from  the   animal 

and  dried  at  a  moderate  temperature,  it  contracts  greatly  by  the 
loss  of  water,  and  its  weight  is  eventually  reduced  to  one-fourth. 

760.  The  Cartilages,  Skin,  and  Membranes. — The  cartilages 
appear  to  have  essentially  the  same  composition  as  the  skin  and 
the  membranes  generally.      They  are  all  composed  of  gelatine 
and  chondrine,  both  of  which  are  entirely  dissolved  by  long  con- 
tinued boiling,  and  form  with  water  a  transparent  jelly.     Their 
exact  composition  has  not  been  fully  determined.     Chondrine  is 
most  abundant  in  the  cartilages. 

The  common  glue  of  commerce  is  dried  gelatine,  and  is  pre- 
pared by  boiling  cuttings  of  parchment,  or  the  skins,  ears,  and 

QUESTIONS. — 759.  What  are  the  muscles  of  animals  ?  What  are  they 
chiefly  composed  of?  760.  What  is  said  of  the  cartilages,  &c.  ?  What 
is  glue  ? 


.      ANIMAL    TISSUES.  499 

hoofs  of  animals,  and  evaporating  the  solution.  Its  use  is  well 
known.  Isinglass,  which  is  a  very  pure  variety  of  gelatine,  is 
prepared  from  the  sounds  of  fish  of  the  genus  acipenser,  especially 
from  the  sturgeon.  The  animal  jelly  of  the  confectioners  is  made 
from  the  feet  of  calves,  the  tendinous  and  ligamentous  parts  of 
which  yield  a  large  quantity  of  gelatine.  .  m 

Gelatine  is  insoluble  in  alcohol,  but  is  dissolved  readily  by  most  of  the 
diluted  acids,  which  form  an  excellent  solvent  for  it. 

Gelatine  manifests  little  tendency  to  unite  with  metallic  oxides.  Cor- 
rosive sublimate  and  acetate  of  lead  do  not  occasion  any  precipitate  in  a 
solution  of  gelatine,  and  the  salts  of  tin  and  silver  affect  it  very  slightly. 

By  boiling  gelatine  with  dilute  sulphuric  acid,  and  precipitating  the 
acid  with  chalk,  a  sweet  crystaline  compound  is  obtained  called  glycocoll 
(glukus,  sweet,  and  kolla,  glue),  or  gelatine  sugar,  the  composition  of 
which  is  C4H5N04. 

The  action  of  tannin  or  tannic  acid  (684)  upon  gelatine  is  peculiar  and 
important,  resulting  in  the'  production,  in  certain  cases,  of  the  well 
known  and  most  useful  substance,  leather. 

Leather  is  usually  formed  by  subjecting  the  skins  of  animals  for  some 
time  to  an  infusion  of  bark  which  contains  a  large  proportion  of  tannic 
acid;  and  the  chief  chemical  change  which  takes  place  is  believed  to 
consist  in  a  union  of  this  acid  with  the  gelatine  of  the  sliin.  This  is  the 
common  leather  of  which  shoes  are  made :  other  varieties  of  this  useful 
manufacture  are  prepared  by  different  modes.  Glove-leather,  for  instance, 
is  prepared  by  impregnating  the  skin,  after  having  been  deprived  of  all 
its  fatty  matter  by  soaking  in  a  weak  alkali,  with  solution  of  common 
salt  and  alum,  from  which  chloride  of  aluminum  is  formed,  and  unites 
with  the  gelatine  of  the  skin. 

The  Brain  and  Nerves. — The  substance  of  the  brain,  nerves, 
and  spinal  marrow  differs  from  that  of  all  other  animal  textures. 
The  white  and  gray  portions  differ  essentially  in  their  nature, 
but  are  composed  chiefly  of  water,  albumen,  a  fatty  matter,  and 
traces  of  phosphates  and  other  salts.  Only  about  one-fifth  of  the 
whole  is  solid  matter.  The  fatty  matter  is  peculiar,  and  is  quite 
unlike  that  of  other  parts  of  the  system.  The  phosphorus  in  the 
brain  is  said  to  amount  to  3  or  4  per  cent,  of  all  the  solid  matter 
contained  in  it. 

761.  The  Bones. — The  bones  of  animals  consist  of  earthy 
matter,  which  is  chiefly  phosphate  and  carbonate  of  lime,  and 
animal  matter,  which  is  essentially  the  same  as  cartilage.  These 

QUESTIONS. — What  is  said  of  the  action  of  tannic  acid  upon  gelatine  ? 
How  is  leather  prepared?  761.  What  is  said  of  the  composition  of  tho 
bones? 


bOO  THE  .BLOOD. 

may  easily  be  separated  from  each  other.  To  separate  the  solid 
or  earfctf  matter,  it  is  only  necessary  to  digest  the  bone  for  a  time 
in  dilute  hydrochloric  acid,  in  which  both  the  phosphate  and 
carbonate  of  lime  are  soluble,  so  that  they  will  be  entirely  re- 
moved, leaving  the  cartilage  soft  and  flexible,  but  retaining 
perfectly  the  fbrm^of  ihe  bone.  The  cartilage  may  be  removed 
by  heating  the  bone  some  time  in  the  open  air,  so  as  to  burn 
away  all  the  organic  matter  j  or  by  digesting  it  in  solution  of  an 
alkali,  or  in  water  at  a  high  temperature,  under  pressure.  In 
some  cases  of  disease,  as  rickets,  to  "which  children  and  youth  are 
chiefly  liable,  there  is  a  deficiency  of  earthy  ^matter  in  the  bones; 
and  they  are,  in  consequence,  weak,  and  incapable  of  affording  the 
necessary  support  to  the  system. 

Horn  differs  from  bone  in  containing  only  a  trace  of  earth.  It  consists 
chiefly  of  gelatine  and  a  cartilaginous  substance  like  coagulated  albumen. 
The  composition  &f  the  nails  and  hoofs  of  animals  is  similar  to  that  of 
horn ;  and  the  cuticle  belongs  to  the  same  class  of  substances. 

702.  The  hair*  seems  to  have  essentially  the  same  composition  as  horn, 
but  the  color  is  occasioned  by  an  oil,  which  is  soluble  to  ether,  and  may 
therefore  be  removed  by  it.  It  contains  sulphur,  and  is  therefore  black- 
ened by  nitrate  of  silver,  or  other  metallic  salt.  . 

When  horn  or  hair  is  heated,  it .  is  first  fused,  and  then  swells  up, 
giving  off  carbonate  of  ammonia,  and  carburetted  hydrogen,  the  last 
of  which  takes  fire,  and  burns  with  a  brilliant  flame. 

Shells  are  composed  of  a  mixture  of  phosphate  and  carbonate  of  lime. 
The  shells  of  the  Crustacea,  as  lobsters,  crabs,  &c.,  usually  contain  4  or 
6  per  ^ent.  of  phosphate  of  lime,  and  50  or  60  per  cent,  of  the  carbonate, 
the  rest  being  animal  matter.  The  shells  of  the  molusca,  as  the  oyster 
and  clam,  are  nearly  pure  carbonate  of  lime,  containing  only  a  mere 
trace  of  animal  matter. 


THE     BLOOD. — PHENOMENA     OF     RESPIRATION 
AND    DIGESTION. 

763,  The  support  of  life  in  animals  is  attended  by  many  chemical 
phenomena,  which  are  constantly  taking  place  in  every  part  of  the 
body,  but  especially  in  the  blood,  the  lungs,  the  digestive  system, 
and  in  the  glands.  The  substances  taken  into  the  mouth  are 
modified  in  the  process  of  digestion,  and  distributed  to  every  part 

QUESTIONS.  —  How  does  horn  differ  in  composition  from  bones  ? 
702.  What  is  said  of  hair?  763.  What  is  said  of  the  chemical  changes 
which  take  place  in  the  system  ? 


THE    BLOOD.  501 

by  the  circulation  of  the  blood,  where  they  come  in  contact  with 
oxygen  received  from  the  air  in  the  lungs.  Among  these  dif- 
ferent principles,  received  in  the  processes  of  nutrition  and  respi- 
ration, important  chemical  changes  are  taking  place,  by  which  the 
animal  heat  is  kept  up,  and  the  waste  of  all  the  various  tissues 
supplied,  and,  indeed,  all  the  animal  functions  supported. 

The  blood  of  the  different  orders  of  animals  is  not  the  same, 
but  we  propose  here  to  speak  of  that  of  the  higher  orders,  or 
vertebrated  animals,  in  which  it  is  always  of  a  red  color. 

In  these,  the  blood  which  i's  brought  from  the  lungs,  and  pro- 
pelled by  the  heart  through  the  arteries  to  every  part  of  the 
system,  is  of  a  bright  red  or  scarlet  color,  and  is  called  arterial 
blood  ;  but  as  it  is  returned  to  the  heart  by  the  veins,  to  be  again 
sent  to  the  lungs,  it  is  of  a  dark  red  or  purple,  and  is  called  venous 
blood.  The  blood  is  therefore  of  two  kinds ;  but,  chemically, 
they  seem  to  be  essentially  the  same. 

The  Blood.  , 

764,  Composition  of  the  Blood.  —  The  blood  is  easily  dis 
tinguished  from  all  the  other  fluids  by  its  color.  Its  taste  is 
slightly  saline,  its  odor  peculiar,  and  to  the  touch  it  seems  some- 
what unctuous.  Its  specific  gravity  is  variable,  but  usually  about 
1-05  ;  and  in  man  its  temperature  is  about  98°  or  100°.  While 
flowing  in  its  vessels,  or  when  recently  drawn,  it  appears  to  the 
naked  eye  as  a  uniform  homogeneous  liquid;  but  if  examined 
with  a  microscope  of  sufficient  power,  numerous  particles  of  a 
discoid  form  are  seen  floating  in  a  nearly  colorless  liquid.  Most 
of  these  discs  are  red,  and  in  the  blood  of  man  are  about  -g^^th 
of  an  inch  in  diameter,  and  one-fourth  as  thick;  but  there  are 
also  others  which  are  without  color.  The  figure  on  next  page 
represents  these  discs  in  human  blood,  as  seen  under  the  micro- 
scope,— a  and  b  colorless  discs.  The  figure  at  the  right  repre- 
sents these  discs  as  they  are  sometimes  seen  united  in  rolls  like 
pieces  of  coin. 

QUESTIONS. — Is  the  blood  the  same  in  all  animals  ?  What  two  kinds 
of  blood  are  there?  764.  What  is  said  of  the  composition  of  the  blood? 
How  does  it  appear  when  viewed  by  the  microscope  ?  What  is  the  form 
of  these  corpuscles?  Their  size? 


502 


THE    BLOOD 


Discs  in  Human  Blood. 

These  discs  vary  considerably  in  size  in  the  blood  of  different 
animals,  being  considerably  smaller  in  the  blood  of  the  common 
domestic  animals  than  in  man,  but  larger  and 
of  an  oval  form  in  oviparous  vertebrates.  They 
are  larger  in  the  blood  of  the  elephant  (see 
%ure  m  tne  nlargin)  than  in  that  of  any  other 
mammalian  species. 


Discs  jn  the  Blood  of 
,  the  Elephant. 


765.  When  the  blood  is  withdrawn  from  the 
system,  these  discs  or  globules  contract  into  a 
solid  mass  or  coagulum,  which,  by  standing, 
entirely  separates  from  the  liquid  serum.  This 
is  a  'thin  yellowish  liquid,  of  sp.  gr.  about 
l-03,Xhid  coagulates  when  heated  to  about  140°.  It  has  a  slight 
alkaline  reaction,  owing  to  the  presence  of  soda,  and  contains  a 
considerable  quantity  of  albumen. 

In  the  living  body  the  blood  also  contains  fibrine  in  solution, 
which,  however,  soon  separates  from  the  coagulum  after  its 
extraction  from  the  system.  Various  salts  also  are  found,  as 
common  salt,  phosphates  of  lime,  magnesia,  and  ammonia,  and 
lactates  of  soda  and  magnesia. 

The  relative  proportion  of  the  ingredients  of  the  blood  must  neces- 
sarily vary,  independently  of  disease,  even  in  the  same  individual, 
according  as  the  nutrition  is  scanty  or  abundant.  Slight  variations  are 
^.Iso  occasioned  by  difference  of  age  and  sex. 


QUESTIONS. — 765.  What  change  occurs  in  the  blood  when  withdrawn 
from  tho  system?  What  substances  are  mentioned  as  contained  in  the 
Xood? 


PHENOMENA    OP    DIGESTION. 

The  following  table  contains  the  results  of  several  analyses  of  blood :— • 

Water 90-5 

Albumen 8-0 

Chlorides  of  sodium  and  potassium. -6 

Lactate  of  soda  and  extractive  matter -4 

Soda  and  phosphate  of  soda *41 

Loss , -09 

100-00 

The  coloring-matter  of  the  blood  is  confined  entirely  to  the  discs  or 
corpuscles  spoken  of  above,  and  has  been  called  hematosine.  In  many 
of  its  properties  it  closely  resembles  albumen.  It  is  composed  of  carbon, 
hydrogen,  nitrogen,  "oxygen,  and  iron,  the  latter  of  which  constitutes 
between  six  and  seven  per  cent. 

766.  Coagulation  of  the  Blood. — The  coagulation  of  the  blood, 
to  which  allusion  has  already  been  made  (765),  consists  in  the 
agglutination  of  the  fibrine  it  contains,  by  which  the  red  globules, 
and  other  suspended  particles,  are  inclosed,  forming  the  clot. 
The  time  required  for  the  coagulation  of  the  blood  depends  much 
upon  temperature,  being  promoted  by  heat  and  retarded  by  cold. 

The  process  is  also  influenced  by  exposure  to  the  air.  If  atmo- 
spheric air  be  excluded,  as  by  filling  a  bottle  completely  with 
recently-drawn  blood,  and  closing  the  orifice  with  a  good  stopper, 
coagulation  is  retarded.  It  is  singular,  however,  that  if  blood  be 
confined  within  the  exhausted  receiver  of  an  air-pump,  the  coagu- 
lation is  accelerated.  *. 

Some  substances,  introduced  into  the  blood,  either  retard  or 
entirely  prevent  its  coagulation,  as  saturated  solution  of  chloride 
of  sodium,  hydrochlorate  of  ammonia,  nitre,  and  a  solution  of 
potassa.  The  coagulation,  on  the  contrary,  is  promoted  by  alum 
and  the  sulphates  of  the  oxides  of  ?inc  and  copper.  The  blood 
of  persons  who  have  died  a  sudden,  violent  death,  by  some  kinds 
of  poison,  or  from  mental  emotion,  is  usually  found  in  a  fluid  state. 

Phenomena  of  Digestion. 

767.  Digestion  is  the  process  by  which  the  food  is  fitted  to 
nourish  the  system,  and  supply  the  constant  waste  that  is  required 
for  the  support  of  the  powers  of  life.     The  blood  is  the  agent  by 

QUESTIONS.— What  is  the  coloring-matter  of  the  blood  called  ?  766.  What 
is  eaid  of  the  coagulation  of  the  blood  ?  767.  What  is  digestion  ? 


504  PHENOMENA    OF    DIGESTION. 

which  the  matter  required  for  the  support  of  the  system  is  sup- 
plied to  the  various  parts  where  it  is  needed ;  but  it  is  from  the 
food  that  it  is  first  received. 

768,  The  Saliva. — The  saliva  is  a  slightly  viscid  liquid,  se- 
creted by  several  glands  about  the   mouth,  called  the  salivary 
glands.     It  serves  to  keep  the  mouth  constantly  moist;  and  the 
sight,  or  even  thought  of  food,  causes  it  to  flow  rapidly  in  the 
mouth.     Besides  water,  and  a  small  quantity  of  several  salts,  it 
contains  a  peculiar  principle  called  ptydline^  which  may  be  pre- 
cipitated from  it  by  absolute  alcohol. 

T-he  use  of  the  saliva  is  to  mix  with  the  food  during  masti- 
cation, and  form  a  soft,  pulpy  mass,  suitable  to  be  swallowed. 
Probably  it  aids  also  in  the  process  of  digestion,  by  fitting  the 
food  to  be  more  readily  acted  on  by  the  juices  of  the  stomach. 

The  saliva  is  often  much  affected  by  disease,  and  occasions  the  bad 
taste  in  the  mouth,  especially  on  rising  in  the  morning.  In  some 
diseases,  as  intermittent  fever,  it  is  often  very  acid. 

769.  The   Gastric  Juice. — The  gastric  juice  is  an  acid  fluid 
secreted  by  the  coats  of  the   stomach,  and  contains  in  solution 
several  salts,  mucus,  albumen,  and  a  nitrogenized  substance  called 
pepsine.     It  has  the  property  of  softening  down  and  dissolving, 
more  or  less  perfectly,  all  the  various  substancss  which  serve  for 
food.     When  the  food  is  introduced  into  the  stomach,  it  is  there 
intimately  mixed  with  this  juice,  by  the  agency  of  which  it  is 
converted   into   a   semi-fluid   matter  called    chyme.      That   this 
change  is  owing  to  the  solvent  power  of  the  gastric  juice  has  been 
fully  determined ;  and  it  seems  to  be  well  established  as  a  further 
fact,  that  the  gastric  juice  secreted  in  the  stomachs  of  animals 
of  any  species  is  especially  adapted  for  dissolving  the  particular 
kind  of  food  upon  which  the  species  usually  feed. 

While  the  food  is  in  the  stomach,  it  is  constantly  kept  in 
motion  by  a  peculiar  movement  of  the  muscular  walls  of  the 
intestine,  called  its  peristaltic  motion.  This  has  the  effect 
thoroughly  to  mix  every  part,  and  also  to  propel  the  mass  slowly 
forward. 

QUESTIONS. — 768.  Describe  the  saliva.  What  purpose  does  it  serve? 
769.  By  what  is  the  gastric  juice  secreted  ?  What  purpose  does  it  serve' 
What  is  chyme  ? 


PHENOMENA    OF    DIGESTION.  505 

The  chyme,  as  it  passes  from  the  stomach,  appears  as  a  homo- 
geneous, semi-fluid  mass;  but  it  has  recently  been  found  that 
the  solvent  action  of  the  gastric  juice  is  chiefly  limited  to  the 
nitrogenized  part  of  the  fluid,  as  the  albumen,  fibrine,  &c. ;  the 
non-nitrogenized  parts,  as  the  starchy  and  fatty  compounds,  being 
only  mechanically  divided  and  mixed  up  with  the  mass. 

From  the  stomach,  the  chyme  pass-as  to  a  large  intestine  called 
the  duodenum,  where  it  is  subjected  to  the  action  of  two  other 
fluids,  the  bile  and  the  pancreatic  juice.,  which  we  will  now  pro- 
ceed to  consider. 

770.  The  Bile. — The  bile  is  a  liquid  secreted  by  the  liver,  and 
preserved  in  the  gall-bladder,  which,  when  the  stomach  is  filled, 
is  slightly  pressed  and  made  to  discharge  its  contents  through  a 
small  duct  into  the  duodenum.     It  is  of  a  yellow,  or  greenish- 
yellow  color,  and  has  a  peculiar  sickening  odor,  and  a  taste  at  first 
sweet  and  then  bitter,  but  exceedingly  nauseous.     Its  consistence 
is  variable,  being  sometimes  limpid,  but  more  commonly  viscid 
and  ropy.     It  contains  a  peculiar  principle  called  cholesterine,  and 
two  organic  acids  called  the  cholic,  and  choleic,  both  of  which  are 
in  combination  with  soda. 

It  seems  now  to  be  very  well  determined  that  one,  if  not  the  chief, 
purpose  served  by  the  bile  is  to  aid  in  the  digestion  of  the  fatty  and  oily 
substances  taken  for  food.  In  connection  with  the  pancreatic  juice,  it 
also  aids  in  the  separation  of  the  chyle. 

Biliary  calculi  are  concretions  which  occasionally  form  in  the  gall- 
bladder, or  duct  leading  from  it.  They  differ  much  in  composition,  but 
not  unfrequently  they  are  composed,  in  great  part,  of  cholesterine. 

771.  The  Pancreatic  Juice. — This  is  a  secretion  of  a  certain 
organ  'called  the  pancreas.      It  is  a  limpid,  colorless,  alkaline 
liquid,  with  a  saltish  taste,  like  that  of  the  serum  of  the  blood. 
It  is  slightly  viscous,  and  coagulates  by  heat,  and  by  the  acids. 

The  pancreatic  juice  is  poured  into  the  duodenum  at  the  same 
time  with  the  bile.  Both  of  these  liquids  act  energetically  upon 
fatty  and  amylaceous  substances,  and  produce  important  changes 

QUESTIONS. — What  fluids  are  poured  into  the  blood  next  after  it  leaves 
the  stomach?     770.  By  what  organ  is  the  bile  secreted?     Describe  it. 
What  compounds  are  contained  in  it?     What  purpose  is  served  by  it? 
771.  What  is  the  character  of  the  pancreatic  juice? 
43 


506  PHENOMENA    OF    RESPIRATION. 

in  them,  by  which  they  are  prepared  to  enter  into  the  circulating 
system. 

We  have  seen  that  the  substances  taken  for  food,  after  having 
been  acted  upon  in  the  stomach  by  the  gastric  juice,  and  reduced 
to  a  homogeneous  mass  called  chyme,  pass  into  the  duodenum, 
where  the  mass  receives  the  bile  and  the  pancreatic  juice ;  imme- 
diately a  change  takes  place,  and  a  milky  liquid  appears  diffused 
through  the  mass,  called  chyle.  This  is  the  part  of  the  food, 
which,  by  the  digestive  process,  has  been  prepared  forthe  nourish- 
ment of  the  system,  the  rest  being  thrown  off  as  refuse  matter; 
and,  as  the  mass  passes  on  through  the  intestinal  canal,  it  is 
absorbed  by  numerous  little  tubes  opening  into  its  side,  called 
lacteals,  and  conveyed  by  them  to  a  common  reservoir,  the  thoracic 
duct.  From  this  it  is  discharged  into  the  left  subclavian  vein, 
and  becomes  incorporated  with  the  blood,  forming  a  part  of  its 
substance,  and  fitting  it  for  the  proper  continuance  of  its  functions. 

Phenomena  of  Respiration. 

772.  All  organized  bodies  require  constantly  the  presence  of 
atmospheric  air  for  the  proper  performance  of  their  various  func- 
tions, and  their  continued  existence  in  the  living  state.  All  the 
larger  land-animals  are  provided  with  lungs,  in  which,  by  the 
action  of  certain  muscles,  air  is  constantly  inhaled  and  again 
expelled,  and  thus  a  continued  circulation  is  kept  up;  but  in 
some  of  the  smaller  ones,  as  insects,  the  breathing  is  by  tubes 
called  trachea,  or  is  performed  by  the  whole  surface  of  their 
bodies.  In  fishes,  certain  organs  called  gills  perform  the  office 
of  lungs,  and  the  air  that  is  breathed  is  first  absorbed  by  the 
water,  and  from  this  imparted  to  the  animal.  In  every  case  the 
process  by  which  the  air  is  made  to  perform  its  office  upon  the 
living  being  is  called  respiration. 

The  important  chemical  changes  that  attend  the  respiration 
of  animals  are,  the  constant  absorption  of  oxygen,  and  the  forma- 
tion and  evolution  of  carbonic  acid. 


QUESTIONS. — What  is  the  chyle?  What  purpose  does  it  serve?  How 
is  it  conveyed  to  the  blood  ?  772.  Do  all  organized  bodies  require  the 
constant  presence  of  air  ?  What  purpose  is  served  by  the  lungs  of  ani- 
mals ?  What  important  changes  attend  the  respiration  of  animals  ? 


PHENOMENA    OP    RESPIRATION.  507 

To  show  the  presence  of  carbonic  acid  in  the  air 
expelled  from  the  lungs,  it  is  only  necessary  to  apply 
a  small  tube  to-  the  mouth,  and  blow,  a  few  seconds, 
into  some  recently-prepared  lime-water ; — the  carbonic 
acid  in  the  air  from  the  lungs  will  unite  with  the  lime, 
forming  carbonate  of  lime,  which  gives  the  solution  a 
milky  appearance.  It  is  true,  there  is  a  little  carbonic 
acid  in  the  air  before  it  is  taken  into  the  lungs ;  but  while 
there  the  quantity  is  very  considerably  increased.  This 
is  shown  satisfactorily  by  blowing  in  the  same  manner 

by  a  hand-bellows  into  another  portion  of  lime-water, 

when  it  will  be  found  that  a  much  longer  time  will  be       Blowing  through 
required  to  produce  the  milkiness  alluded  to  (304).  Lime-water. 

773.  The  change  in  the  blood  from  the  venous  to  the  arterial 
state,  is  effected  in  the  living  animal  during  the  passage  of  the 
blood  through  the  capillary  vessels  of  the  lungs,  where  it  is 
exposed  to  the  action  of  an  extensive  surface  of  atmospheric  air, 
through  the  thin  membranes  which  separate  these  from  the  air- 
vessels  ;  and  the  arterial  blood,  in  traversing  the  capillary  system 
of  the  body,  imparting  nourishment  to  it,  gradually  assumes  the 
dark-colored  condition  in  which  it  is  returned  to  the  heart  by  the 
veins.  The  same  change  is  produced  when  venous  blood,  just 
taken  from  the  system,  is  brought  in  contact  with  atmospheric 
air,  and  is  attended  with  the  evolution  of  carbonic  acid  gas.  It 
takes  place  more  speedily  when  air  is  agitated  with  blood ;  it  is 
still  more  rapid  when  pure  oxygen  is  substituted  for  atmospheric 
air ;  and  it  does  not  occur  at  all  when  oxygen  is  entirely  excluded. 
The  quantity  of  carbonic  acid  developed  very  exactly  corresponds 
with  that  of  the  oxygen  which  disappears. 

The  quantity  of  oxygen  withdrawn  from  the  atmosphere,  and  of  car- 
bonic acid  disengaged,  is  variable  in  different  individuals,  and  in  the 
same  individual  at  different  times,  depending  very  much  upon  the  state 
of  the  system.  In  a  state  of  health,  anything  that  accelerates  the  respi- 
ration increases  the  amount  of  oxygen  absorbed,  and  the  quantity  of  car- 
bonic acid  exhaled  ;  but  in  certain  cases  of  disease,  as  in  inflammatory 
fevers,  though  the  respiration  may  be  very  rapid,  little  oxygen  is  with- 
drawn from  the  air,  and  the  venous  blood  is  found  to  be  very  florid. 


QUESTIONS. — How  may  the  presence  of  carbonic  acid  in  the  air  ex- 
haled from  the  lungs  be  shown?  773.  How  is  the  change  in  the  blood 
from  the  venous  to  the  arterial  state  effected  ?  What  change  is  again 
produced  in  the  blood  as  it  circulates  through  the  system  ? 


508  PHENOMENA    OF    RESPIRATION. 

774.  Animal  Heat. — Nutrition. — It  has  long  been  known  that 
there  is  a  close  connection  between  the  function  of  respiration, 
and  the  development  of  heat  in  the  animal  system. 

Thus,  in  all  animals  whose  respiratory  organs  are  small  and 
imperfect,  and  which,  therefore,  consume  but  a  comparatively 
minute  quantity  of  oxygen,  and  generate  little  carbonic  acid,  the 
temperature  of  the  blood  varies  with  that  of  the  medium  in  which 
they  live.  In  warm-blooded  animals,  on  the  contrary,  in  which 
the 'respiratory  apparatus  is  larger,  and  the  chemical  changes  more 
complicated,  the  temperature  is  almost  uniform  ;  and  those  have 
the  highest  temperature  whose  lungs,  in  proportion  to  the  size 
of  their  bodies,  are  largest,  and  which  consume  the  greatest 
quantity  of  oxygen.  The  temperature  of  the  same  animal  at 
different  times  is  connected  with  the  state  of  the  respiration. 
When  the  blood  circulates  sluggishly,  and  the  temperature  is 
low,  the  quantity  of  oxygen  consumed  is  comparatively  small ; 
but,  on  the  contrary,  a  large  quantity  .of  that  gas  disappears  when 
the  circulation  is  brisk  and  the  power  of  generating  heat  energetic. 
It  has  also  been  observed,  that  when  an  animal  is  placed  in  a  very 
warm  atmosphere,  so  as  to  require  little  heat  to  be  generated 
within  his  own  body,  the  consumption  of  oxygen  is  unusually 
small. 

We  have  seen  already  that  the  digestion  of  the  food  is  per- 
formed, in  part,  in  the  stomach,  by  the  gastric  juice  dissolving 
the  nitrogenized  or  albuminous  portion,  and  partly  in  the  duode- 
num, where  the  amylaceous  and  fatty  parts  are  acted  on  by  the 
bile  and  pancreatic  juice.  This  indicates  an  important  division 
of  the  substances  taken  for  food  into  two  kinds ;  and  we  find  that 
the  same  distinction  is  also  observed  in  the"  purposes  they  serve 
in  the  system.  It  has  been  determined  that  the  albuminous  or 
nitrogenized  parts  of  the  food,  go  to  support  the  waste  of  the 
tissues,  while  the  non-nitrogenized  parts,  as  starch,  sugar,  and 
the  fats  and  oils,  are  consumed  in  preserving  the  temperature 


QUESTIONS.  —  774.  Is  there  any  immediate  connection  between  the 
function  of  respiration  of  animals  and  the  temperature  of  their  systems  ? 
What  facts  are  mentioned  as  illustrating  and  proving  the  point?  What 
two  purposes  are  served  by  the  food?  What  are  the  elements  of  respi 
ration  and  nutrition  ? 


PHENOMENA     OF    RESPIRATION. 

of  the  system.     The  latter  may  therefore  be  called  the  elements 
of  respiration,  and  the  former  elements  of  nutrition. 

775.  The  combustion  of  carbon  and  hydrogen  in  the  open  air, 
as  is  well  known,  is  always  attended  by  the  evolution  of  heat; 
and  the  same  effect  is  produced  in  the  system  when  these  sub- 
stances unite  with  the  oxygen  introduced  into  the  blood  in  the 
process  of  respiration.     The  only  essential  difference  is,  that  in 
combustion  the  process  is  more  rapid,  and  the  heat  produced  pro- 
portionally more  intense;   but  the  absolute  quantity  of  heat  pro- 
duced  by  the    consumption   of  a   given    amount  of   carbon    or 
hydrogen  is,  in  all  probability,  always  the  same. 

We  here  find  the  origin  of  the  carbonic  acid  which  is  given 
off  during  respiration,  and  also  by  the  insensible  perspiration 
from  the  skin,  while  the  water  produced  by  the  combustion  of  the 
hydrogen  unites  with  the  large  quantity  ever  present  in  all  parts 
of  the  body. 

We  see,  therefore,  that  the  oxygen  of  the  air  is  tending  to  consume  all 
living  beings,  as  really  as  if  they  were  in  a  burning  fire ;  in  fact,'  this 
consumption,  which  is  a  kind  of  combustion,  is  ever  going  on  while 
respiration  continues.  To  keep  up  the  combustion,  a  constant  supply 
of  fuel  is  needed,  which  is  found  in  the  respiratory  food,  as  before 
stated ;  and  when  these  elements  enter  into  combination  within  the  ani- 
mal system,  heat  is  as  necessarily  developed  as  when  the  same  thing 
takes  place  in  the  open  air,  in  ordinary  combustion. 

776.  Use  of  the  Fat  in  the  Animal  Economy. — The  fat  and 
oils  found  in  animals  appear  to  be  stores  of  respiratory  food,  laid 
up  by  a  wise  foresight  of  nature  for  time  of  need.     Thus,  it  is 
well  known   that  when  food  is   abundant  the  fat  accumulates, 
which  is  again  gradually  wasted  away  when  the  supply  of  food 
becomes  deficient.     When  the  supply  of  food  is  wholly  withheld 
from  an  animal,  the  fat  rapidly  disappears,  its  carbon  and  hydrogen 
going  to  supply  the  demands  of  respiration ;  and  when  this  has 
all  been   consumed,   the   substance   of  the  muscles  is  attacked, 
which  become  lean  and  flaccid,  and  lose  their  contractile  power; 
and  at  length  the  brain  and  nerves  yield  to  the  same  influence, 

QUESTIONS. — 775.  What  always  attends  the  combustion  of  carbon  and 
hydrogen  ?  Is  the  same  effect  produced  in  the  animal  system  ?  776.  What 
purpose  is  served  by  the  fat  in  the  animal  system  ?  What  becomes  of  the 
fat  when  the  supply  of  food  is  short  ? 

43* 


5l6  ANIMAL     SUBSTANCES. 

and  death  speedily  closes  the  scene  of  suffering*  In  animals  that 
lie  torpid  during  the  winter,  nature  has  provided  that  in  the  sum- 
mer season  a  large  accumulation  of  fat  is  laid  up  to  supply  the 
demands  of  respiration  during  the  time  they  lie  torpid  in  their 
dens;  and,  on  the  approach  of  the  warm  weather  of  spring,  they 
are  consequently  found  lean  and  weak. 

It  is  important  to  observe  that  the  composition  of  the  nitrogenized  food 
consisting  chiefly  of  the  proteine  compounds  and  gelatine,  is  the  same  a 
that  of  many  of  the  tissues,  the  waste  of  which  it  supplies ;  and  it  is  the 
opinion  of  many  that  these  compounds  are  never  produced  in  the  anima! 
system,  but  are  appropriated  directly  from  the  food,  unchanged. 

It  is,  however,  known  that  some  substances  are  formed  in  the  system 
from  the  materials  supplied  by  the  food.  Thus,  it  has  been  found  that  a 
lean  goose,  fed 'on  Indian  corn,  will  in  a  few  days  increase  in  weight 
several  pounds,  in  consequence  of  the  fat  that  will  be  formed  in  the  sys- 
tem, which  must  have  been  contained  in  the  corn,  or  formed  from  the 
substance  of  the  corn  by  the  organs  of  the  animal.  Now  that  the  most 
of  it  has  been  formed  in  the  latter  mode  is  certain  from  the  fact  that  all 
the  oil  or  fatty  matter  contained  in  the  corn  will  amount  only  to  a  small 
fraction  of  the  fat  found  in  the  goose.  So  bees  will  form  wax  when  fed 
on  pure  honey  or  pure  sugar.  It  has  been  found  by  experiment  that  foi 
twenty  parts  of  honey  consumed  they  will  form  about  one  part  of  wax. 


SEVERAL    ANIMAL    SECRETIONS    AND    EXCRE- 
TIONS   NOT    BEFORE    NO-TIC  ED. 

777.  Milk.  —  This  well-known  liquid  is  secreted  by  females 
of  the  class  mammalia,  for  the  support  of  their  young.  It  is  of  a 
white  color,  and  is  a  little  heavier  than  water,  usually  having  a 
density  from  1-02  to  1-04.  Its  composition  varies  in  different 
animals,  and  also  in  the  same  animal,  according  to  the  food  that 
is  taken.  On  an  average,  that  of  the  cow  contains,  in  an  hun- 
dred parts,  water  874  parts;  butter,  4-0;  milk-sugar,  or  lactine, 
and  soluble  salts,  5-0;  caseine,  albumen,  and  insoluble  salts,  3-6. 

When  milk  is  examined  by  a  microscope,  it  is  found  to  be  a 
transparent  liquid,  with  numerous  minute  globules  floating  in  it, 
which  consist  chiefly  of  fatty  matter,  and  which,  if  the  milk  stand 
at  nest  a  few  hours,  rise  to  the  surface  as  cream.  If,  now,  the 
cream  is  separated,  and  violently  agitated  for  a  time,  the  mem- 

QUBSTIONS. — 777.  What  substances  are  contained  in  cow's  milk.  What 
is  cream  ? 


ANIMAL    SUBSTANCES.  511 

branes  enveloping  these  fatty  corpuscles  are  broken,  and  it  collects 
into  a  mass  of  butter,  which  floats  in  the  watery  liquid. 

Milk  is  not  coagulated  by  heat,  but  this  effect  is  readily  pro- 
duced by  acids  and  by  rennet,  which  is  prepared  by  soaking  the 
inner  coat  of  a  calf's  stomach  in  water.  The  coagulum  so  formed 
is  called  curd,  and  when  pressed  and  otherwise  prepared,  con- 
stitutes cheese. 

778.  When  milk  is  allowed  to  stand  some  hours,  at  a  tempera- 
ture of  between  60°  and  70°,  it  sours;  and,  on  examination,  a 
peculiar  acid  is  found  in  it  called  lactic  acid,  the  composition  of 
which  is  C6H606.      When   highly  concentrated,   it  is  a  thick, 
colorless  liquid,  of  specific  gravity  1-21,  and  has  a  very  sour  taste. 
It  is  soluble  in  alcohol  and  water,  but  cannot  be  crystalized. 

Lactic  acid  may  also  be  formed  fforn  sugar  by  mixing  with  it 
in  solution  some  curds  from  milk,  and  some  chalk  to  unite  with  it 
as  it  is  produced,  and  allowing  the  whole  to  stand  for  some  time 
at  a  temperature  of  about  80°.  The  chemical  change  that  takes 
place  appears  to  be  very  simple,  as  an  atom  of  fruit-sugar  contains 
exactly  the  ingredients  of  two  atoms  of  lactic  acid.  Thus, 
C,2H,20,2  =  2(C6H606).  It  is  this  acid  which  is  contained  in 
the  gastric  juice. 

Lactic  acid  is  also  formed  when  the  juices  of  beets,  carrots,  &c., 
are  allowed  to  ferment  at  high  temperatures.  At  the  same  time 
a  viscid,  slimy  substance  is  formed,  from  which  circumstance  this 
has  been  termed  the  viscous  fermentation. 

Milk  may  also  be  made  to  undergo  the  vinous  or  alcoholic 
fermentation.  For  this  purpose  it  is  exposed  for  some  hours  to 
a  temperature  of.  about  100°;  and  the  alcohol,  which,  no  doubt, 
is  formed  from  the  milk-sugar  it  contains,  may  subsequently  be 
distilled  from  it.  It  has  long  been  known  that  some  barbarous 
nations  are  accustomed  to  prepare  an  intoxicating  drink  from 
milk,  by  some  fermenting  process. 

779.  Lymph. — Lymph  is  a  watery  fluid,  secreted  by  many  of 
the  membranes;  it  lubricates  all  the  cavities,  and  moistens  the 

QUESTIONS. — 778.  What  acid  is  formed  in  the  souring  of  milk?  May 
.it  be  formed  from  sugar?  May  milk  be  made  to  undergo  the  alcoholic 
fermentation  ?  779.  What  is  lymph  ? 


512  ANIMAL    SUBSTANCES. 

cellular  tissues  of  the  body.  It  much  resembles  the  serum  of  the 
blood,  and  mixes  readily  with  water.  Sometimes,  in  diseases, 
this  liquid,  or  a  liquid  analogous  to  it,  is  secreted  in  one  or  more 
organs,  so  abundantly  as  to  constitute  dropsy. 

780,  Urine. — This  is  a  yellowish  liquid,  secreted  by  the  kid- 
neys, by  which  various  substances,  constantly  accumulating  in  the 
blood,  are  separated  from  it  during  the  healthy  state  of  the  sys- 
tem. This  excretion  is  essential,  as  without  it  the  substances 
thus  thrown  off  would,  in  a  short  time,  accumulate  in  such  quantity 
as  to  destroy  life.  It  has  usually  a  specific  gravity  of  about  1-02, 
and  consists  of  water,  holding  in  solution  a  small  portion  of  urea 
and  several  different  salts,  as  well  as  a  little  free  acid,  from  which 
it  acquires  an  acid  reaction.  A  little  mucus  is  also  usually  pre- 
sent, derived  from  the  urinary  passages ;  and  in  consequence  of 
this  it  putrefies  if  kept  for  a  time  at  a  summer  temperature. 

The  quantity  of  the  urine  is  affected  by  various  causes,  espe- 
cially by  the  nature  and  quantity  of  the  food  and  the  liquids 
received  into  the  stomach ;  but  on  an  average,  a  healthy  person 
voids  between  thirty  and  forty  ounces  daily.  The  quality  of  this 
fluid  is  likewise  influenced  by  the  same  circumstances,  being  some- 
times in  a  very  dilute  state,  and  at  others  highly  concentrated. 

The  urine  of  birds,  insects,  and  reptiles,  is  solid,  and  consists 
chiefly  of  urate  of  ammonia.  Guano,  which  has  been  so  largely 
imported  within  a  few  years,  to  be  used  as  a  manure,  is  composed 
chiefly  of  the  urine  and  other  excrements  of  birds,  which  have 
been  collecting  for  ages  in  the  places  where  they  are  found.  It  is 
imported  chiefly,  if  not  entirely,  from  islands  on  the  coast  of 
Africa,  and  the  west  coast  of  South  America. 

781.  Urea,  C2H4N202  =  CyO,NH3  +  HO.— This  substance  is 
always  found  in  healthy  urine,  and  may  also  be  prepared  arti- 
ficially. Its  crystals,  when  pure,  are  transparent  and  colorless, 
of  a  slight  pearly  lustre,  and  have  commonly  the  form  of  a  four- 
sided  prism.  It  leaves  a  sensation  of  coldness  on  the  tongue,  like 

QUESTIONS. — 780.  What  purpose  is  served  in  the  animal  system  by  the 
secretion  of  the  urine?  What  is  guano?  781.  From  what  is  urea 
obtained  ? 


ANIMAL     SUBSTANCES.  513 

nitre,  and  its  -smell  is  faint  and  peculiar,  but  not  urinous.  Its 
specific  gravity  is  about  1-35. 

Water,  at  60°,  dissolves  more  than  its  own  weight  of  urea,  and 
boiling  water  takes  up  an  unlimited  quantity.  It  requires  for 
solution  about  five  times  its  weight  of  alcohol  at  60°,  and  rather 
less  than  its  own  weight  at  a  boiling  temperature.  The  aqueous 
solution  of  pure  urea  is  very  permanent,  but  if  the  other  con- 
stituents of  urine  are  present,  it  putrefies  with  rapidity,  and,  by  a 
heat  of  250°,  it  is  melted  and  resolved  into  carbonate  of  ammonia, 
and  other  products. 

Though  urea  has  not  any  distinct  alkaline  properties,  it  unites 
with  the  nitric  and  oxalic  acids,  forming  sparingly  soluble  com- 
pounds, which  crystalize  in  scales  of  a  pearly  lustre. 

Urea  is  prepared  artificially  as  follows.  Four  parts  of  dry  Prussiate 
of  potash  are  intimately  mixed  with  2  parts  of  peroxide  of  manganese, 
and  heated  to  dull  redness  in  an  iron  vessel.  When  the  mass  has  become 
cold  it  is  digested  in  cold  water,  and  frequently  stirred,  until  all  that  is 
soluble  is  taken  up  by  the  water.  This  is  now  decanted,  and  mixed  with 
3  parts  of  sulphate  of  ammonia  previously  dissolved  in  water.  Sulphate 
of  potash  and  cyanate  of  ammonia  are  at  once  formed ;  and  on  the  applica- 
tion of  a  moderate  heat  the  latter  compound  is  converted  into  urea,  which 
is  only  an  isomeric  modification. 

To  separate  the  urea,  the  whole  solution  is  evaporated  to  dryness,  and 
the  urea  taken  up  by  strong  alcohol. 

782.  Uric  Acid,  doIIjN^Oe,  is  found,  in  combination  with  bases, 
in  the  urine  of  many  animals,  especially  that  of  birds  of  prey,  and 
of  serpents.  It  is  a  white,' tasteless,  and  inodorous  solid,  but  sparingly 
soluble  in  either  cold  or  hot  water.      Urate  of  ammonia  consti- 
tutes a  large  part  of  the  best  guano. 

When  uric  acid  is  boiled  with  peroxide  of  lead-  a  substance  called 
allantoine  is  formed,  which  has  the  composition,  C8H6N408,  carbonic  acid 
being  also  evolved.  It  is  a  solid,  and  capable  of  being  crystalized. 
Boiled  with  the  strong  acids,  it  forms  urea  and  allantofc  acid,  C6H4N206.. 
Alloxan,  alloxantine,  alloxanic,  and  dialuric  acids,  are  other  closely  allied 
substances. 

783.  Besides  the  above  substances,  there  is  found  in  the  urine 
of  herbivorous  animals,  as  the  cow  and  horse,  another  important 

QUESTIONS. — Describe  the  artificial  mode  of  preparing  urea.  782,  What 
is  uric  acid  ?  783.  From  what  is  hippuric  acid  obtained  ? 


514  ANIMAL    SUBSTANCES. 

acid,  called  the  hippuric  acid  (from  hippos,  horse).     Its  com- 
position is  C18H9N06  =  C18H8NO&+  HO. 

To  prepare  this  acid,  the  fresh  urine  may  be  concentrated  by  a 
gentle  heat, — taking  care  not  to  cause  it  to  boil, — until  its  volume 
is  diminished  one-half;  and  hydrochloric  acid  then  added  until 
an  acid  reaction  is  produced.  By  standing  for  a  time,  impure 
hippuric  acid  will  make  its  appearance  in  the  form  of  long,  slender 
crystals.  These  arc  then  to  be  redissolved  in  boiling  water,  mixed 
with  some  milk  of  lime  and  animal  charcoal,  and  the  resulting 
solution  of  hippurate  of  lime  carefully  filtered  before  cooling. 
To  decompose  this,  hydrochloric  acid  is  to  be  added  until  an  acid 
reaction  appears;  and,  on  cooling,  the  pure  hippuric  acid  will  be 
obtained  in  beautiful  crystals.  These  are  only  slightly  insoluble 
in  cold,  but  very  soluble  in  boiling  water. 

Some  of  the  relations  of  this  acid  are  curious  and  important.  When 
boiled  for  some  time  with  a  strong  acid,  it  is  converted  into  benzole  acid 
and  glycocoll  (760),  2  atoms  of  water  being  absorbed  in  the  process. 
Thus, 

C18H9N06  -f  2HO  =  C]4H604  -f  C4H5N04. 

By  boiling  with  peroxide  of  lead,  hippuric  acid  is  converted  into  benza- 
mide  (634),  carbonic  acid  and  water  being  formed  at  the  same  time. 

The  action  of  nitrous  acid  upon  the  hippuric,  results  in  the  production 
of  a  new  acid,  called  the  benzogly collie,  which  has  the  formula,  C^H^O^; 
water  and  nitrogen  being  eliminated.  Glycocoll  acted  on  by  nitrous  acid 
forms  gtycocollic  acid,  C8H8Ojj. 


QUESTIONS. — Describe  the  process  of  obtaining  hippuric  acid.     When 
it  is  boiled  with  a  strong  acid,  what  compounds  are  formed  from  it  ? 


APPENDIX. 


Tables  of  Weights  and  Measures,  Proportion  of  Alcohol  in 
Spirits  of  different  Specific  Gravities,  etc. 

WEIGHTS. 

English  Imperial  Standard  Troy  Weight. 
24  Grains  =  1  Pennyweight. 

20  Pennyweights  =  1  Ounce  =  480  Grains. 
12  Ounces  =  1  Pound  =  5760  Grains. 

Apothecaries'  Weight. 
20  Grains      =  1  Scruple  9. 

3  Scruples  =r  1  Drachm  5- 

8  Drachms  =.  1  Ounce  g  r=  480  Grains. 
12  Ounces     =  1  Pound    =5760  Grains. 
The  Grain,  Ounce,  and  Pound  are  the  same  iu  both  the  above  weights. 

Avoidupois  Weight. 
1  Drachm    =  27-34  Grains. 
16  Drachms  =  1  Ounce  r=  437 -5  Grains. 
16  Ounces     =  1  Pound  =  7000  Grains. 
28  Pounds     —  1  Quarter. 

4  Quarters  =  1  Cwt.  or  112  Ibs. 
20  Cwt.          =  1  Ton. 


French  Decimal  Weights. 


Gramme          =  15-443  Grains. 
Decigramme    =  -1-544 
Centigramme  =    0-154 
Milligramme  =    0-015 


Gramme  =  15-443  Grains. 

Decagramme  =  10  Grammes  =  154-43  « 
Hectogramme  =  100  "  =  1544-3  " 
Kilogramme  =  1000  «  =  15443-  « 


The  Kilogramme  =  2-206  Ibs.  Avoid.,  and  2-68  Ibs.  Troy. 

Troy  weight  is  used  in  all  cases  in  weighing  the  precious  metals,  the  ounce  being  gene- 
rally made  the  unit.  Physicians,  in  making  their  prescriptions,  and  druggists,  in  com- 
pounding their  medicines,  make  use  of  the  subdivisions  of  the  pound  called  Apothecaries' 
weight ;  but  drugs  are  always  bought  and  sold  by  Avoirdupois  weight. 

In  scientific  researches,  as  in  chemical  analysis,  and  the  determination  of  specific 
gravities,  either  Troy  weight  or  the  French  decimal  system  is  used.  When  Troy  weight 
is  used,  the  grain  is  made  the  unit. 

MEASURES  OF  CAPACITY. 

Wine  or  Apothecaries'  Measure. 
60  Drops       =  1  Drachm  5. 

8  Drachms  =:  1  Ounce  g. 
16  Ounces     =  1  Pint. 
8  Pints        =  1  Gallon  =  231  Cubic  Inches. 
The  cubic  inch  of  pure  water  at  62°  weighs  252-458  grains,  or  16-283  grammes. 

French  Decimal  Measure. 
Litre         =  61-025  Cubic  Inches. 
Decilitre    =    6-102  « 

Centilitre  =    0-610  « 

Millilitre  =    0-061          « 
The  Litre  =  1-056  quart  wine  measure. 

MEASURES  OF  LENGTH. 
French  Decimal  System. 
Metre  =  39-371  Inches. 

Decimetre  =  3-937  '* 
Centimetre  =  -393  « 
Millimetre  =  -039  « 

The  French  Metre  is  one  ten  millionth  part  of  the  distance,  upon  the  surface  of  the 
earth,  from  the  equator  to  either  pole. 

The  Gramme  (the  unit  of  weight)  is  the  weight  of  a  cubic  centimetre  of  pure  water,  at 
its  greatest  density.  (515) 


516 


APPENDIX. 


TABLE  showing  the  Specific  Gravity  of  Liquids,  at  the  Temperature  of 
65°  Fahr.y  corresponding  to  the  Degrees  of  Baumfs  Hydrometer. 


FOR  LIQUIDS  LIGHTER  THAN  WATER. 

Deg.    Sp.  Gr. 
10  =  1-000 
11          -990 
12          -985 
13          -977 
14          -970 
15          -963 
16          -955 

Deg.       Sp.  Gr. 
17    =   -949 
18          -942 
19          -935 
20          -928 
21          -922 
22          -915 

Deg.      Sp.  Gr. 
23    =  -909 
24          -903 
25          -897 
28          '892 
27          -886 
28          -880 

Deg.      Sp.  Gr. 
29    =  '874 
30          -867 
31          -861 
•32          '856 
33          '852 
34          -847 

Deg.       Sp.  Gr. 
35    =  -842 
36          -837 
37          -832 
38          -827 
39          -822 
40          -817 

FOR  LIQUIDS  HEAVIER  THAN  WATER. 

Dug.     Sp.  Gr. 
0    =   1-000 
3          1-020 
6          1-040 
9          1-064 
12          1-089 

Deg.      Sp.  Gr. 
15    =  1-114 
18          1-140 
21          1-170 
24          1-200 
27          1-230 

Deg.       Sp.  Gr. 
30    =  1-261 
33          1-295 
36          1-333 
39          1-373 
42          1-414 

Deg.       Sp.  Gr. 
45    =  1-455 
48          1-500 
51          1-547 
54          1-594 
57          1-659 

Deg.       Sp.  Gr. 
60    =  1-717 
63          1-779 
66          1-848 
69          1-920 
72          2-000 

TABLE  showing  the  Quantity  of  Absolute  Alcohol  in  (100  parts  of)  Spirits 
of  different  Specific  Gravities,  at  60°  Fahr.,  the  spirits  being  supposed  to 
contain  nothing  but  pure  alcohol  and  pure  water. 


ALCOHOL. 

8P.  GRAVITY. 

ALCOHOL. 

8P.  GRAVITY. 

ALCOHOL. 

SP.  GRAVITY. 

100 

0-796 

66 

0-881 

32 

0-955 

99 

0.798 

65 

0-883 

31 

0-957 

98 

0-801 

64 

0-886 

30 

0-958 

97 

0-804 

63 

0-889 

29 

0-960 

96 

0-807 

62 

0-891 

28 

0-962 

95 

0-809 

61 

0-893 

27 

0-963 

94 

0-812 

60 

0-896 

26 

0-965 

93 

0-815 

59 

0-898 

25 

0-967 

02 

0-817 

58 

0-900 

24 

0-968 

91 

0-820 

67 

6-902 

23 

0-970 

90 

0-822 

56 

0'904 

22 

0-972 

•    89 

0-825 

55 

0-906 

21 

0-973 

88 

0-827 

64 

0-908 

20 

0-974 

87 

0-830 

63 

0-910 

19 

0-975 

86 

0-832 

62 

0-912 

18 

0-977 

85 

0-835 

61 

0-915 

17 

0-978 

84 

0-838 

50 

0-917 

16 

0979 

83 

0840 

49 

0-920 

15 

0-981 

82 

0-843 

48 

0-922 

14 

0-982 

81 

0-846 

47 

0-924 

13 

0-984 

80 

0-848 

46 

0-926 

12 

0-986 

79 

0-851 

45 

0-928 

11 

0-987 

78 

0-853 

44 

0-930 

10 

0-988 

77 

0-855 

43 

0-933 

9 

0-989 

76 

0-857 

42 

0-935 

8 

0-990 

75 

0-860 

41 

0-937 

7 

0-991 

74 

0-863 

40 

0-939 

6 

0-992 

73 

0-865 

39 

0-941 

6 

0-993 

72 

0-867 

38 

0943 

4 

0-994 

71 

0-870 

37 

0-945 

3 

0-996 

70 

0-872 

36 

0-947 

2 

0-998 

69 

0-874 

35 

0-949 

1 

0'999 

68 

0-875 

34 

'0-951 

0 

67 

0-879 

33 

0-953 

INDEX. 


Acetal ; 424 

Acetamide 480 

Ace-tone...... 427 

Acetonitriles 480 

Acids,  coupled 422 

defined 153 

metallic 347 

vinic 433 

Acid,  acetic 423 

acetous 423 

acetonic 459 

aconitic 467 

adipic 459 

aldehydic 423 

alloxanic 513 

anisic 452 

antimonic 366 

arsenic 252 

arsenious 251 

aspartic 479 

auric 388 

benzoglycocollic 514 

benzoic 448 

benzylic 449 

boracic 283 

bromic 219 

butyric 359 

cacodylic ; 475 

campholic ;...  454 

camphoric 454 

capric 459 

caproic 459 

caprylic 459 

carbolic 451 

carbonic 263 

cerotic 462 

44 


Acid,  chloric 211 

chlorous 210 

choleic , 505 

cholic 605 

chromic 358 

cinnamic 451 

citraconic 467 

citric 467 

cobaltocyanic 490 

coumaric 454 

cyanic 481 

cyanuric.... 484 

dialuric 513 

ethalic 461  - 

ferric , 355 

fluoboracic 283 

fluosilicie 280 

formic 428 

fumaric 468 

fulmenic 482 

gallic 469 

geic 415 

glycocollic 514 

blppuric 513 

humic 415 

hydriodic 217 

hydrobromic 219 

hydrochloric 211 

hydrocyanic 484 

hydroferrocyanic 487 

hydroferridcyanic 488 

hydrofluoric 221 

hydrofluosilicic 281 

hydrosulphocyanic » 485 

hydrosulphuric 234 

hydrotelluric 241 

hypochloric 210 

(517) 


518 


INDEX. 


Acid,  hypochlorous 210 

hyponitrous 199 

hypophosphoric 245 

hyposulphuric 225 

hypo  sulphurous 225 

iodic 217 

iodous 217 

isotinic 471 

isotartario 467 

itaconitic 467 

lactic 511 

malic 468 

manganic 347 

margaric 456,  458 

melissic 462 

meconic 469 

metacetonic 427 

metagallic 469 

metaphosphoric 247 

metatartaric 467 

nmcic 411 

muriatic 211 

myronic 452 

nitric 200 

nitrous 199 

oenanthylic 459 

oleic.... 456,  458 

oxalic * 466 

oxamic 440 

palmitic 460 

paramaleic 468 

paratartaric 467 

pectic 411 

pelargonic 459 

perchloric 211 

periodic 217 

permanganic 348 

phosphoric 246 

phosphorous 245 

phosphogly eerie 457 

pimelic 459 

propionic 427 


PAQl 

Acid,  propylic 427 

Prussic 484 

pyrogallic 469 

pyroligneous 417,  424 

*  pyrophosphoric 247 

racemic , 467 

ricinoleic 460 

salicilic 450 

salicilous 450 

sebacic 459 

selenic 240 

selenous 240 

silicic 279 

stannic 363 

stearic..... .456,  457 

suberic 459 

succinic 459 

sulpharsenic 253 

sulpharsenious 253 

sulphethalic , 460 

sulphindigotic 477 

sulphindylic 477 

sulphocarbonic 276 

sulphocyanic , 485 

sulphogly eerie 457 

sulphomethylic 441 

sulphovinic 435 

sulphuric 228 

sulphurous 225 

tannic 468 

tartaric 466 

telluric v 241 

tellurous 241 

ulmic 415 

uric 513 

valerianic 431 

Acroleine 457 

Affinity 158 

Agate 279 

Air,  atmospheric 192 

empyreal 174 

fixed 263 


INDEX. 


519 


Air   inflammable 181 

vital 174 

Alabaster 335 

Aldehyde 422 

amylic 431 

Albite 342 

Albumen 492 

Alcargen 475 

Alcarsine 475 

'Alcohol,  acrylic 432 

amylic 432 

butyric 402,  403 

caprylic 460 

cerotic 462 

melissic 462 

methylic 428 

phenylic 432,  450 

sulphur 432 

•wine 418 

Algaroth,  powder  of 367 

Alizarine 437 

Alkali,  volatile 202 

Allanite »  344 

Allantoine 513 

Allotropism l&T 

Alloxan 513 

Alloxantine 513 

Alum 341 

Alumina 340 

ALUMINUM 339 

Amalgams 376 

Amber 464 

Amides".....- 478 

Ammelide 486 

Ammeline 486 

Ammonia 202 

Ammonium 819 

Amylene 443 

Amygdaline 448 

Amylamine 473 

Anatase , 373 

Anchor  ice 29 

Aniline 473 


Anhydrite v. 335 

Animal  heat 511 

Anisene 452 

Anthracite 258,  259 

ANTIMONY 365 

Aquafortis 201 

regia 213 

Archil 477 

Argol '.... 466 

Arrow-root 407 

ARSENIC 250 

Ashes 259 

Asparagine 471,  479 

Asphaltum 416 

Astatic  needle 116 

Atmosphere 192 

Atomic  theory 150 

Atoms 14 

specific  heat  of 151 

Attraction 14 

Aurum  musivum 364. 

Azote...  191 


Balloons ; - 184 

Balsam,  Canada 463 

Peru. 451 

Tolu 451 

Ballistic  pendulum 307 

Barilla 315 

BARIUM 328 

Baryta,  barytes 328 

Batteries,  galvanic 92 

Bees' -wax , 461 

Bell-metal 372 

Benzamide 448 

Benzene 449 

Benzile 449 

Benzoine 449 

Benzone 449 

BERYLLUM 344 

Biliary  calculi 605 

Bile -  &0* 


520 


INDEX 


Bisethyle  

PAGE 

474 

PAGH 

4.RO 

BISMUTH  

367 

4^4. 

Black  lead  

258 

471 

flux  

290 

A  p.  A. 

336 

Caproine 

45fi    4^0 

Blonde  

359 

AK.R     4KQ 

Blood  

501 

4AQ 

Blowpipe  

..180,  273 

47ft 

187 

Cartilage 

498 

41 

OKfi 

Bologna  vial...  

327 

412 

Bones  .... 

499 

333 

Borax  

316 

Cerite  

344 

344 

4.91 

462 

ran  y  

079 

Cetine  

460 

478 

347 

Brir>V<a 

qjo 

..257,  260 

407 

Cheese  

511 

366 

Chemical  equivalents  

..*.....  155 

218 

China  ware  

342 

442 

Chloanthite  

364 

372 

Chloral  

427 

471 

206 

447 

441 

Butter 

459 

..;....  478 

456  459 

265 

Butyrone         •   

460 

Cholesterine  

505 

Butyronitriie.  •••  

480 

359 

iron  

357 

359 

CHROMIUM  

357 

Cacodyle 

.  .   .     474 

372 

Cadet's  fuminsj  liquid  •     . 

.  .      475 

Chyle  

505 

362 

Chyme                

504 

471 

470 

Calaniine                   • 

.  359  362 

374 

331 

Cinnamene.    

451 

Calcedony  ...»  

279 

Cinnamon  

451 

377 

Clav 

343 

Camphene          

.  .  ..  446 

172 

454 

169 

..  447 

Cleavelandite  ... 

..  342 

INDEX. 


521 


PAGE 

Clouds 64 

Coal 257 

tar 417 

COBALT 251,364 

Cochineal ., 478 

Codeine 470 

Coke 259 

Colcothar 357 

Collodion 414 

COLUMBIUM 374 

Columbite 374 

Combination,  laws  of 143 

Combustion 179 

of  iron 174 

Compound  bodies 14 

radicals 396 

blowpipe 187 

Conjugated  compounds 401 

Copal 463 

COPPER 371 

pyrites ~ 372 

variegated 372 

1  vitreous 372 

Copperas 356 

Corrosive  sublimate 378 

Cotton 413 

gun , 414 

Coumarine 454 

Coupled  compounds 401 

Cream 510 

of  tartar 467 

Creosote 417 

Cryolite 339 

Cryophorus 49 

Crystalography 158 

Cupel 382 

Curd 511 

Cyamelide . 484 

Cyamethene 482 

Cyanogen 275 

D 

Daguerreotype 72 

De  la  Rive's  ring 119 

•  44* 


Derbyshire  spar 343 

Dew 52 

Dextrine 407 

Diachylon 463 

Diallogite 348 

Diamond 258 

Diamagnet 112 

Diaspore 340 

Diastase 407 

DIDYMIUM 344 

Dimorphism 170  . 

Dioptase 373 

Dipping-needle 114 

Distillation 47 

Drummond  light 188 

Dutch  gold 372 

E 

Earths , 328 

alkaline 339 

Ebullition 41 

Elaldehyde 423 

Electricity 74 

atmospheric 85 

conduction  of 76 

distribution  of 80 

induction  of 78 

nature  of 74 

thermo 85 

of  chemical  action...     87 

theories  of 74 

sources  of 81 

Electrodes 92 

Electro-magnet 125 

Electro-magnetic  engine 127 

telegraph 133 

Electrometer 76 

Electro-metallurgy 109 

Electrophorus -. 84 

Electrotype 109 

Elements.... 137 

classification  of. 172 

Emery 340 

Empyreal  air 174 

Emulsion 448 


522 


INDEX. 


Enamel 324 

Engine*  electro-magnetic 127 

Epsom  salt 338 

ERBIUM 344 

Ethal 456,  451 

Ethers 433 

hydrobromic 438 

hydrochloric 437 

sulphuric 433,  434,  438 

Ether,  acetic 439 

amylic 443 

benzoic ^49 

butyric 459 

carbonic 439 

cyanic 482 

cyanuric 484 

formic 440 

hydriodic 438 

hydrocyanic 438 

hydrosulphuric 438 

hyponitrous 438 

methylic 440 

nitric 439 

oxalic 440 

salicylic. .' 451 

sebacic 459 

silicic 439 

stearic 458 

wood 440 

acetic  methylic 443 

benzoic  methylic 449 

hydriodic  methylic 442 

hydrobromic  methylic...  442 
hydrochloric  methylic...  441 
hydrosulphuric  methylic  442 

nitric  methylic 442 

oxalic  methylic 443 

salicylic  methylic 451 

stearic  methylic 458 

sulphuric  methylic 443 

acetic  amylic 444 

hydriodic  amylic 444 


Ether,  hydrochloric  amylic 444 

hydrosulphuric  amylic...  444 

oxalic  amylic 444 

Ethylamine 472 

Ethylammonium 472 

Eudiometers 193 

Eupione 417 

Evaporation 44 

Expansion  of  gases 22 

liquids...... 21 

solids 19 

F 

Fats 455 

Fecula 405 

Feldspar 342 

Fermentation,  acetic 423 

butyric 460 

vinous 418 

viscous 511 

Fibrine 491 

Fire-damp 267,  415 

syringe. 60 

Fixed  air 263 

oils 455 

Flame 270 

Flint 279 

FLUORINE 220 

Fluor-spar 220,  333 

Flux,  black 290 

Fly-powder 251 

Formula,  Ohm's. 100 

Freezing  mixtures 38 

point 21 

Fusel  oil 430 

G 

Gadolinate 344 

Galena 368 

Galvanoscope 117,  121 

Galvanic  batteries 92 

Galvanometer 87 

Gastric  juice 504 


INDEX. 


52S 


Geine 415 

Gelatine 498 

German  silver 365 

Germination  of  seeds 494 

Gibbsite 340 

Gin 421 

Glass 322 

Glauber's  salt 314 

Glucina 344 

GLUCINUM 344 

Glucose 409 

Glue 498 

Gluten 492 

Glycerine 456 

Glycocoll 498 

GOLD ; 386 

Graphite 257 

Green,  Scheele's 255 

verditer 377 

Grenockite 362 

Guano 512 

Gum  Arabic 411 

elastic , 464 

Senegal 411 

tragacanth 411 

Gun  cotton 414 

powder 306 

Gutta  percha 463 

Gymnotus  electricus 101 

Gypsum 334 

H 

Hail 54 

Hair  ..., 500 

Hartshorn 202 

Heat,  absorption  of 34 

animal '. 508 

capacity  for 58 

conduction  of 29 

convection  of 3 

nature  of 17 

radiation  of 33 

reflection  of 

relative 58 

sources  of....  1 


Heat,  specific 68 

transmission  of 35 

Heavy  spar 330 

Hematite 349 

Hematosine 502 

Hematoxyline 478 

Hepar  sulphuris 304 

Homologous  bodies 401 

Honey 409 

Horn 500 

quicksilver  378 

silver 384 

Humus 415 

Hydragethyle 474 

Hydrates 198 

HYDROGEN 181 

Hygrometers 52 


Iceland  spar 334 

Illuminating  gas  * 269 

India  rubber 464 

Indigo 476 

Indigotine 476 

Inflammable  air 181 

Ink,  indelible 385 

sympathetic 364 

writing 468 

IODINE 215 

lodofofm 442 

IRIDIUM ••••  392 

IRON , 348 

pyrites... 222 

Isatine 471 

Isinglass 499 

Isomerism 157 

Isomorphism 159 


Jet 


259 


Kaolin 342 

Kermes  mineral 367 

King's  yellow 253 


5!M 

L 
Lac  ,  

INI 

PAGE 

463 
510 
476 
261 
344 
196 
143 
308 
426 
424 
499 
418 
477 
493 
407 
318 
435 
79 
68 
65 
73 
60 
65 
65 
62 
61 
85 
413 
259 
331 
334 
54 
370 
318 
318 
477 
304 
349 
478 
385 
510 

477 
125 

>EX. 

PAGS 

337 
338 
111 
125 
113 
114 
126 
114 
132 
373 
479 
345 
410 
410 
497 
334 
43 
458 
458 
369 
464 
486 
486 
462 
486 
432 
432 
374 
427 
423 
400 
109 
443 
430 
472 
510 
410 
347 
373 
416 
370 
408 
373 
373 

Likes  

Lauffhinsr  seas 

Magnetism  of  earth  k  

Laws  of  combination    .  .     .  . 

terrestrial  

Magneto-electric  machine  

LEAD  .          . 

extractof  

sugar  of  

Leather  469, 

Leaven  

Mflrhip 

Loyden  jar  

Light,  decomposition  of  

double  refraction  of  

Melissine...  

Mellon  

theories  of  

Mercaptans  ,  

Mercaptides  

MERCURY,  

Lithia 

Metlrylal  

Milk                 

Lunar  caustic  

Lymph  

M 
Madder  

Molybdenite  •  

Magic  circle  

INDEX, 


525 


Monasite 344 

Mordants 476 

Morphia,  Morphine 469 

Mortar 333 

Mosaic  gold 364 

Muscles 498 

Myricine 461 

Myrosine 452 

Myrtle  wax 461 

N 

Naphtha 416 

Naphthalene 417 

Naphthaline r. 417 

Narcotine 470 

Nascent  state 205 

Natron 319 

NICKEL 365 

Nicotine 470 

Nitre 305 

Nitriles 480 

NITROGEN 194 

Nomenclature 151 

Nutgalls .' 468 

Nutrition 508 


Ohm's  formula 100 

Oil  of  aniseed 452 

bitter  almonds 448 

cinnamon 451 

cumin 452 

cloves 452 

elemi 447 

garlic 453 

juniper 447 

lemons 447 

mustard,  black 452 

pepper 447 

peppermint 452 

pimento 452 

spiraea  ulmaria 450 

turpentine 446 

vitriol  228 


PAGB 

Oil  of  winter  green 451 

Oil,  castor 460 

fusel 430 

Oleine 456 

Opium 469 

Orcine 477 

Organic  bodies 393 

Orpiment 253 

Orthite 344 

OSMIUM , 391 

Oxamide 440 

OXYGEN...  ,.  174 


PALLADIUM 392 

Palmatine 460 

Pancreatic  juice 505 

Paracyanogen 481 

Paraffine 417 

Paramylene 443 

Paris  green 373 

Pearlash 304 

Peat 415 

Pectine 411 

PELOPIUM 374 

Pendulum,  ballistic , 307 

Pepsine 504 

Petalite 342 

Petroleum 416 

Pewter 369 

Phenol 450,  417 

PHOSPHORUS 241 

Photography „     70 

Photometers 63 

Picrotoxine 471 

Pinchbeck ,...  374 

Piperine , 471 

Pitchblende 374 

Plasters 463 

Plaster  of  Paris 334 

PLATINUM 389 

Plumbago 258,  356 

Polymerism 157 


526 


INDEX. 


Porcelain 342 

Potassa,  Potash 301 

POTASSIUM 298 

Potato  oil 430 

Propione .427 

Prussian  blue 489 

Ptyaline 604 

Pulse  glass 50 

Purple  of  Cassius 389 

Purpurine 477 

Pyroacetic  spirit 427 

Pyrochlore 344 

Pyrolusite 347 

Pyrometer 27 

Pyroxylic  spirit 417,  428 

Pyroxyline 414 

Q 

Quartz 279 

Quercitrine 478 

Quicklime 331 

Quicksilver 374 

Quinia,  Quinine 470 

K 

Bain 54 

Rats-bane 251 

Realgar 253 

Red  lead 370 

precipitate 377 

Prussiate  of  potash 488 

Register  thermometer 25 

Repulsion 13 

Resin ,  463 

Respiration  of  animals 506 

plants 495 

RHODIUM 392 

Rocelinine >..  477 

Rochelle  salt 467 

Rock  candy 408 

Rock  oil 466 

Rosin 463 

Rotation  of  crops 497 


Ruby 340 

Rum 421 

Rupert's  drops 327 

RUTHENIUM 892 

Rutile 373 

S 

Safety  lamp 270 

Sago 407 

Salseratus 305 

Sal-ammoniac 321 

mirabile 314 

soda 315 

volatile  j. 321 

Salt,  common 312 

Epsom 338 

Glauber's 314 

microcosmic 322 

rock 312 

Salicine 450 

Saliva 504 

Sandarac 464 

Sapphire 340 

Scheele's  green 255,  373 

Sealing-wax 464 

Selenite 335 

SELENIUM 239 

Seneca  oil 416 

Shells 500 

Silica 279 

SILICON 278 

Silurus  electricus 101 

SILVER 381 

Smalt 364 

Smaltine 364 

Soap 456,  462 

Soda 311 

ash 315 

fountains 265 

SODIUM 310 

Solder , 369 

hard...  ..  372 


INDEX. 


527 


Solar  spectrum 63 

Soluble  glass 280 

Spathic  iron 356 

Specific  gravity  of  atoms 151 

Specular  iron 349 

Speculum  metal 372 

Spelter 360 

Spermaceti 460 

Spheroidal  state  of  liquids...:..     61 

Spinelle 340 

Spirit  of  hartshorn 202 

Mindererus 426 

turpentine 446 

salt 211 

wine 420 

Spirit-lamp 421 

Spodumeme 318,  342 

Springs,  sulphur 235 

Stalactites 334 

Stalagmites 334 

Stanethyle 474 

Starch, 405 

Steam 43 

Stearine 456 

Stearoptens 446 

Steel 353 

Stereotype  plates 335 

Stibethyle 474 

Stibium 365 

Strichnia,  Strichnine 471 

*Strontia 330 

STRONTIUM. 330 

Styrax 451 

Styrole 451 

Substitution 400 

Sugar,  barley 408 

cane 408 

diabetic 409 

grape 409 

milk 410 

of  lead 425 

of  sour  fruits,...          ..  410 


Sulphoform 442 

SULPHUR 222 

springs 235 

Symbols 155 

Synaptase 448 

Sympathetic  ink 364 

T 

Tallow,  bayberry 461 

Tangential  force 114 

Tannin 468 

Tantalite 374 

TANTALUM 374 

Tapioca 407 

Tar 463 

coal 417 

Tartar 466 

cream  of *..  467 

emetic 467 

Telegraph,  electro- magnetic 133 

TELLURIUM 240 

TERBIUM 344 

Terrestrial  magnetism 114 

Theine 471 

Thermography 73 

Thermometers «...  22 

Thorina 344 

Thorite 344 

THORIUM 344 

TIN „ 272 

Tincal 816 

TITANIUM 873 

Tombac » 372 

Tonka  bean 454 

Torpedo 101,  484 

Treacle 408 

Trona 315 

Troostite 373 

TUNGSTEN 373 

Turmeric  root 478 

Turnbull's  blue 489 

Turpentine,  spirits  of 446 


528 


INDEX. 


Turpentine,  oil  of 446 

Turpeth,  mineral. 380 

Turnsol 477 

Type  metal 369 


Ulmine 415 

Upas 471 

Uranite 374 

URANIUM 374 

Urea 482,  512 

Urine...  ..  512 


Valeronitrile 480 

VANADIUM 373 

Vanilla 454 

Vaporization 40 

Verdigris , 426 

Verditer,  green 377 

Vermillion....  ,,, 380 

Vial,  Bologna. 327 

Vinegar 423 

Vinous  fermentation 418 

Viscous        "  511 

Vita,  air 174 

Vitality 14,  394 

Vitriol,  blue 373 

green 356 

white 361 

oil  of 228 

Volatile  alkali 202 

Voltaic  pile 92 


w 

Water 185 

constitutional 296 

of  crystalization 159,  296 

lime 331 

Wax,  bees* 461 

myrtle 461 

Whiskey, 421 

White  lead 376 

Witherite 329 

Wine 466 

Wolfram 373 

Woody  fibre 413 

Wood 411 

Wood  naphtha 428 

spirit 428 

vinegar 424 


Xanthine 477 

Xyloidine 414 


Yeast .418 

Yellow  prussiate  of  potash 487 

chrome 359 

king's 253 

YTTRIUM 344 


Zaffre 364 

ZINO 359 

Zincethyle 474 

Zircon 344 

ZIRCONIUM 344 

Zirconia 344 


THE    END. 


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~T*' 


